Interview Questions On SQL/PLSQL/FORMS & REPORTS/DBA/CONSULTANT
By- What is an oracle instance?
- What is a view?
- What is referential integrity?
- Name the data dictionary that stores user-defined constraints?
- What is a collection of privileges?
- What is a snapshot?
- What is a synonym?
- What is a cursor?
- What is a sequence?
- What is a trigger?
- What is an exception?
- What is a partition of table?
- What are pseudo-columns in SQL? Provide examples.
- What are the Data Control statements?
- What is a schema?
- What is a type?
- What is a data model?
- What is a relation?
- Advantages of redo log files?
- What is an Archiver?
- What is a database buffer cache?
- What are the background processes in Oracle?
- %type and %rowtype are attributes for…?
- What are the steps in a two-phase commit?
- What is a union, intersect, minus?
- What is a join, explain the types of joins?
- What is a co-related sub-query?
- ODBC stands for…?
- Data-type used to work with integers is?
- Describe data models?
- Describe the Normalization principles?
- What are the types of Normalization?
- What is de-normalization?
-
Oracle Interview Questions and Answers
-
What are the components of physical database structure of Oracle database?
- Oracle database is comprised of three types of files. One or more datafiles, two are more redo log files, and one or more control files.
-
What are the components of logical database structure of Oracle database?
- There are tablespaces and database's schema objects.
What is a tablespace?
A
database is divided into Logical Storage Unit called tablespaces. A
tablespace is used to grouped related logical structures together.
What is SYSTEM tablespace and when is it created?
Every Oracle database contains a tablespace named
SYSTEM, which is automatically created when the database is created. The
SYSTEM tablespace always contains the data dictionary tables for the
entire database.
Explain the relationship among database, tablespace and data file ?
Each databases logically divided into one or more
tablespaces one or more data files are explicitly created for each
tablespace.
What is schema?
A schema is collection of database objects of a user.
What are Schema Objects?
Schema objects are the logical structures that directly
refer to the database's data. Schema objects include tables, views,
sequences, synonyms, indexes, clusters, database triggers, procedures,
functions packages and database links.
Can objects of the same schema reside in different tablespaces?
Yes.
Can a tablespace hold objects from different schemes?
Yes.
What is Oracle table?
A table is the basic unit of data storage in an Oracle
database. The tables of a database hold all of the user accessible data.
Table data is stored in rows and columns.
What is an Oracle view?
A view is a virtual table. Every view has a query
attached to it. (The query is a SELECT statement that identifies the
columns and rows of the table(s) the view uses.)
What is Partial Backup ?
A Partial Backup is any operating system backup short of a full backup, taken while the database is open or shut down.
What is Mirrored on-line Redo Log ?
A
mirrored on-line redo log consists of copies of on-line redo log files
physically located on separate disks, changes made to one member of the
group are made to all members.
What is Full Backup ?
A full backup is an operating system backup of all data
files, on-line redo log files and control file that constitute ORACLE
database and the parameter.
Can a View based on another View ?
Yes.
Can a Tablespace hold objects from different Schemes ?
Yes.
Can objects of the same Schema reside in different tablespace ?
Yes.
What is the use of Control File ?
When an instance of an ORACLE database is started, its
control file is used to identify the database and redo log files that
must be opened for database operation to proceed. It is also used in
database recovery.
Do View contain Data ?
Views do not contain or store data.
What are the Referential actions supported by FOREIGN KEY integrity constraint ?
UPDATE and DELETE Restrict - A referential integrity
rule that disallows the update or deletion of referenced data. DELETE
Cascade - When a referenced row is deleted all associated dependent rows
are deleted.
What are the type of Synonyms?
There are two types of Synonyms Private and Public.
What is a Redo Log ?
The set of Redo Log files YSDATE,UID,USER or USERENV SQL functions, or the pseudo columns LEVEL or ROWNUM.
What is an Index Segment ?
Each Index has an Index segment that stores all of its data.
Explain the relationship among Database, Tablespace and Data file?
Each databases logically divided into one or more tablespaces one or more data files are explicitly created for each tablespace
What are the different type of Segments ?
Data Segment, Index Segment, Rollback Segment and Temporary Segment.
What are Clusters ?
Clusters are groups of one or more tables physically stores together to share common columns and are often used together.
What is an Integrity Constrains ?
An integrity constraint is a declarative way to define a business rule for a column of a table.
What is an Index ?
An Index is an optional structure associated with a
table to have direct access to rows, which can be created to increase
the performance of data retrieval. Index can be created on one or more
columns of a table.
What is an Extent ?
An Extent is a specific number of contiguous data
blocks, obtained in a single allocation, and used to store a specific
type of information.
What is a View ?
A view is a virtual table. Every view has a Query
attached to it. (The Query is a SELECT statement that identifies the
columns and rows of the table(s) the view uses.)
What is Table ?
A table is the basic unit of data storage in an ORACLE
database. The tables of a database hold all of the user accessible data.
Table data is stored in rows and columns.
Can a view based on another view?
Yes.
What are the advantages of views?
- Provide an additional level of table security, by restricting access to a predetermined set of rows and columns of a table.
- Hide data complexity.
- Simplify commands for the user.
- Present the data in a different perspective from that of the base table.
- Store complex queries.
What is an Oracle sequence?
A sequence generates a serial list of unique numbers for numerical columns of a database's tables.
What is a synonym?
A synonym is an alias for a table, view, sequence or program unit.
What are the types of synonyms?
There are two types of synonyms private and public.
What is a private synonym?
Only its owner can access a private synonym.
What is a public synonym?
Any database user can access a public synonym.
What are synonyms used for?
- Mask the real name and owner of an object.
- Provide public access to an object
- Provide location transparency for tables, views or program units of a remote database.
- Simplify the SQL statements for database users.
What is an Oracle index?
An index is an optional structure associated with a
table to have direct access to rows, which can be created to increase
the performance of data retrieval. Index can be created on one or more
columns of a table.
How are the index updates?
Indexes are automatically maintained and used by Oracle.
Changes to table data are automatically incorporated into all relevant
indexes.
What is a Tablespace?
A database is divided into Logical Storage Unit called
tablespace. A tablespace is used to grouped related logical structures
together
What is Rollback Segment ?
A Database contains one or more Rollback Segments to temporarily store "undo" information.
What are the Characteristics of Data Files ?
A data file can be associated with only one database.
Once created a data file can't change size. One or more data files form a
logical unit of database storage called a tablespace.
How to define Data Block size ?
A data block size is specified for each ORACLE database
when the database is created. A database users and allocated free
database space in ORACLE data blocks. Block size is specified in
INIT.ORA file and can’t be changed latter.
What does a Control file Contain ?
A Control file records the physical structure of the database. It contains the following information.
Database Name
Names and locations of a database's files and redolog files.
Time stamp of database creation.
What is difference between UNIQUE constraint and PRIMARY KEY constraint ?
A column defined as UNIQUE can contain Nulls while a column defined as PRIMARY KEY can't contain Nulls.
What is Index Cluster ?
A Cluster with an index on the Cluster Key
When does a Transaction end ?
When it is committed or Rollbacked.
What
is the effect of setting the value "ALL_ROWS" for OPTIMIZER_GOAL
parameter of the ALTER SESSION command ? What are the factors that
affect OPTIMIZER in choosing an Optimization approach ?
Answer The OPTIMIZER_MODE initialization parameter
Statistics in the Data Dictionary the OPTIMIZER_GOAL parameter of the
ALTER SESSION command hints in the statement.
What is the effect of setting the value "CHOOSE" for OPTIMIZER_GOAL, parameter of the ALTER SESSION Command ?
The Optimizer chooses Cost_based approach and optimizes
with the goal of best throughput if statistics for atleast one of the
tables accessed by the SQL statement exist in the data dictionary.
Otherwise the OPTIMIZER chooses RULE_based approach.
How does one create a new database? (for DBA)
One can create and modify Oracle databases using the
Oracle "dbca" (Database Configuration Assistant) utility. The dbca
utility is located in the $ORACLE_HOME/bin directory. The Oracle
Universal Installer (oui) normally starts it after installing the
database server software.
One can also create databases manually using scripts. This option,
however, is falling out of fashion, as it is quite involved and error
prone. Look at this example for creating and Oracle 9i database:
CONNECT SYS AS SYSDBA
ALTER SYSTEM SET DB_CREATE_FILE_DEST='/u01/oradata/';
ALTER SYSTEM SET DB_CREATE_ONLINE_LOG_DEST_1='/u02/oradata/';
ALTER SYSTEM SET DB_CREATE_ONLINE_LOG_DEST_2='/u03/oradata/';
CREATE DATABASE;
What database block size should I use? (for DBA)
Oracle recommends that your database block size match,
or be multiples of your operating system block size. One can use smaller
block sizes, but the performance cost is significant. Your choice
should depend on the type of application you are running. If you have
many small transactions as with OLTP, use a smaller block size. With
fewer but larger transactions, as with a DSS application, use a larger
block size. If you are using a volume manager, consider your "operating
system block size" to be 8K. This is because volume manager products use
8K blocks (and this is not configurable).
What are the different approaches used by Optimizer in choosing an execution plan ?
Rule-based and Cost-based.
What does ROLLBACK do ?
ROLLBACK retracts any of the changes resulting from the SQL statements in the transaction.
How does one coalesce free space ? (for DBA)
SMON coalesces free space (extents) into larger,
contiguous extents every 2 hours and even then, only for a short period
of time.
SMON will not coalesce free space if a tablespace's default storage
parameter "pctincrease" is set to 0. With Oracle 7.3 one can manually
coalesce a tablespace using the ALTER TABLESPACE ... COALESCE; command,
until then use:
SQL> alter session set events 'immediate trace name coalesce level n';
Where 'n' is the tablespace number you get from SELECT TS#, NAME FROM SYS.TS$;
You can get status information about this process by selecting from the SYS.DBA_FREE_SPACE_COALESCED dictionary view.
How does one prevent tablespace fragmentation? (for DBA)
Always set PCTINCREASE to 0 or 100.
Bizarre values for PCTINCREASE will contribute to fragmentation.
For example if you set PCTINCREASE to 1 you will see that your extents
are going to have weird and wacky sizes: 100K, 100K, 101K, 102K, etc.
Such extents of bizarre size are rarely re-used in their entirety.
PCTINCREASE of 0 or 100 gives you nice round extent sizes that can
easily be reused. E.g.. 100K, 100K, 200K, 400K, etc.
Use the same extent size for all the segments in a given
tablespace. Locally Managed tablespaces (available from 8i onwards) with
uniform extent sizes virtually eliminates any tablespace fragmentation.
Note that the number of extents per segment does not cause any
performance issue anymore, unless they run into thousands and thousands
where additional I/O may be required to fetch the additional blocks
where extent maps of the segment are stored.
Where can one find the high water mark for a table? (for DBA)
There is no single system table, which contains the high
water mark (HWM) for a table. A table's HWM can be calculated using the
results from the following SQL statements:
SELECT BLOCKS
FROM DBA_SEGMENTS
WHERE OWNER=UPPER(owner) AND SEGMENT_NAME = UPPER(table);
ANALYZE TABLE owner.table ESTIMATE STATISTICS;
SELECT EMPTY_BLOCKS
FROM DBA_TABLES
WHERE OWNER=UPPER(owner) AND SEGMENT_NAME = UPPER(table);
Thus, the tables' HWM = (query result 1) - (query result 2) - 1
NOTE: You can also use the DBMS_SPACE package and calculate the HWM = TOTAL_BLOCKS - UNUSED_BLOCKS - 1.
What is COST-based approach to optimization ?
Considering available access paths and determining the
most efficient execution plan based on statistics in the data dictionary
for the tables accessed by the statement and their associated clusters
and indexes.
What does COMMIT do ?
COMMIT makes permanent the changes resulting from all
SQL statements in the transaction. The changes made by the SQL
statements of a transaction become visible to other user sessions
transactions that start only after transaction is committed.
How are extents allocated to a segment? (for DBA)
Oracle8 and above rounds off extents to a multiple of 5
blocks when more than 5 blocks are requested. If one requests 16K or 2
blocks (assuming a 8K block size), Oracle doesn't round it up to 5
blocks, but it allocates 2 blocks or 16K as requested. If one asks for 8
blocks, Oracle will round it up to 10 blocks.
Space allocation also depends upon the size of contiguous free
space available. If one asks for 8 blocks and Oracle finds a contiguous
free space that is exactly 8 blocks, it would give it you. If it were 9
blocks, Oracle would also give it to you. Clearly Oracle doesn't always
round extents to a multiple of 5 blocks.
The exception to this rule is locally managed tablespaces. If a
tablespace is created with local extent management and the extent size
is 64K, then Oracle allocates 64K or 8 blocks assuming 8K-block size.
Oracle doesn't round it up to the multiple of 5 when a tablespace is
locally managed.
Can one rename a database user (schema)? (for DBA)
No, this is listed as Enhancement Request 158508. Workaround:
Do a user-level export of user A
create new user B
Import system/manager fromuser=A touser=B
Drop user A
Define Transaction ?
A Transaction is a logical unit of work that comprises one or more SQL statements executed by a single user.
What is Read-Only Transaction ?
A Read-Only transaction ensures that the
results of each query executed in the transaction are consistant with
respect to the same point in time.
What is a deadlock ? Explain .
Two processes wating to update the rows
of a table which are locked by the other process then deadlock arises.
In a database environment this will often happen because of not issuing
proper row lock commands. Poor design of front-end application may cause
this situation and the performance of server will reduce drastically.
These locks will be released automatically when a commit/rollback
operation performed or any one of this processes being killed
externally.
What is a Schema ?
The set of objects owned by user account is called the schema.
What is a cluster Key ?
The related columns of the tables are
called the cluster key. The cluster key is indexed using a cluster index
and its value is stored only once for multiple tables in the cluster.
What is Parallel Server ?
Multiple instances accessing the same database (Only In Multi-CPU environments)
What are the basic element of Base configuration of an oracle Database ?
It consists of
one or more data files.
one or more control files.
two or more redo log files.
The Database contains
multiple users/schemas
one or more rollback segments
one or more tablespaces
Data dictionary tables
User objects (table,indexes,views etc.,)
The server that access the database consists of
SGA (Database buffer, Dictionary Cache Buffers, Redo log buffers, Shared SQL pool)
SMON (System MONito)
PMON (Process MONitor)
LGWR (LoG Write)
DBWR (Data Base Write)
ARCH (ARCHiver)
CKPT (Check Point)
RECO
Dispatcher
User Process with associated PGS
What is clusters ?
Group of tables physically stored together because they share common columns and are often used together is called Cluster.
What is an Index ? How it is implemented in Oracle Database ?
An index is a database structure used by
the server to have direct access of a row in a table. An index is
automatically created when a unique of primary key constraint clause is
specified in create table comman (Ver 7.0)
What is a Database instance ? Explain
A database instance (Server) is a set of memory structure and background processes that access a set of database files.
The process can be shared by all users. The memory structure that
are used to store most queried data from database. This helps up to
improve database performance by decreasing the amount of I/O performed
against data file.
What is the use of ANALYZE command ?
To perform one of these function on an index, table, or cluster:
- To collect statistics about object used by the optimizer and store them in the data dictionary.
- To delete statistics about the object used by object from the data dictionary.
- To validate the structure of the object.
- To identify migrated and chained rows of the table or cluster.
What is default tablespace ?
The Tablespace to contain schema objects created without specifying a tablespace name.
What are the system resources that can be controlled through Profile ?
The number of concurrent sessions the
user can establish the CPU processing time available to the user's
session the CPU processing time available to a single call to ORACLE
made by a SQL statement the amount of logical I/O available to the
user's session the amout of logical I/O available to a single call to
ORACLE made by a SQL statement the allowed amount of idle time for the
user's session the allowed amount of connect time for the user's
session.
What is Tablespace Quota ?
The collective amount of disk space available to the objects in a schema on a particular tablespace.
What are the different Levels of Auditing ?
Statement Auditing, Privilege Auditing and Object Auditing.
What is Statement Auditing ?
Statement auditing is the auditing of the powerful system privileges without regard to specifically named objects.
What are the database administrators utilities available ?
SQL * DBA - This allows DBA to monitor
and control an ORACLE database. SQL * Loader - It loads data from
standard operating system files (Flat files) into ORACLE database
tables. Export (EXP) and Import (imp) utilities allow you to move
existing data in ORACLE format to and from ORACLE database.
How can you enable automatic archiving ?
Shut the database
Backup the database
Modify/Include LOG_ARCHIVE_START_TRUE in init.ora file.
Start up the database.
What are roles? How can we implement roles ?
Roles are the easiest way to grant and
manage common privileges needed by different groups of database users.
Creating roles and assigning provides to roles. Assign each role to
group of users. This will simplify the job of assigning privileges to
individual users.
What are Roles ?
Roles are named groups of related privileges that are granted to users or other roles.
What are the use of Roles ?
REDUCED GRANTING OF PRIVILEGES - Rather
than explicitly granting the same set of privileges to many users a
database administrator can grant the privileges for a group of related
users granted to a role and then grant only the role to each member of
the group.
DYNAMIC PRIVILEGE MANAGEMENT - When the privileges of a group must
change, only the privileges of the role need to be modified. The
security domains of all users granted the group's role automatically
reflect the changes made to the role.
SELECTIVE AVAILABILITY OF PRIVILEGES - The roles granted to a user
can be selectively enable (available for use) or disabled (not available
for use). This allows specific control of a user's privileges in any
given situation.
APPLICATION AWARENESS - A database application can be designed to
automatically enable and disable selective roles when a user attempts to
use the application.
What is Privilege Auditing ?
Privilege auditing is the auditing of the use of powerful system privileges without regard to specifically named objects.
What is Object Auditing ?
Object auditing is the auditing of accesses to specific schema objects without regard to user.
What is Auditing ?
Monitoring of user access to aid in the investigation of database use
How does one see the uptime for a database? (for DBA )
Look at the following SQL query:
SELECT to_char (startup_time,'DD-MON-YYYY HH24: MI: SS') "DB Startup Time"
FROM sys.v_$instance;
Marco Bergman provided the following alternative solution:
SELECT to_char (logon_time,'Dy dd Mon HH24: MI: SS') "DB Startup Time"
FROM sys.v_$session
WHERE Sid=1 /* this is pmon */
/
Users still running on Oracle 7 can try one of the following queries:
Column STARTED format a18 head 'STARTUP TIME'
Select C.INSTANCE,
to_date (JUL.VALUE, 'J')
|| to_char (floor (SEC.VALUE/3600), '09')
|| ':'
-- || Substr (to_char (mod (SEC.VALUE/60, 60), '09'), 2, 2)
|| Substr (to_char (floor (mod (SEC.VALUE/60, 60)), '09'), 2, 2)
|| '.'
|| Substr (to_char (mod (SEC.VALUE, 60), '09'), 2, 2) STARTED
from SYS.V_$INSTANCE JUL,
SYS.V_$INSTANCE SEC,
SYS.V_$THREAD C
Where JUL.KEY like '%JULIAN%'
and SEC.KEY like '%SECOND%';
Select to_date (JUL.VALUE, 'J')
|| to_char (to_date (SEC.VALUE, 'SSSSS'), ' HH24:MI:SS') STARTED
from SYS.V_$INSTANCE JUL,
SYS.V_$INSTANCE SEC
where JUL.KEY like '%JULIAN%'
and SEC.KEY like '%SECOND%';
select to_char (to_date (JUL.VALUE, 'J') + (SEC.VALUE/86400), -Return a DATE
'DD-MON-YY HH24:MI:SS') STARTED
from V$INSTANCE JUL,
V$INSTANCE SEC
where JUL.KEY like '%JULIAN%'
and SEC.KEY like '%SECOND%';
Where are my TEMPFILES, I don't see them in V$DATAFILE or DBA_DATA_FILE? (for DBA )
Tempfiles, unlike normal datafiles, are not listed in v$datafile or dba_data_files. Instead query v$tempfile or dba_temp_files:
SELECT * FROM v$tempfile;
SELECT * FROM dba_temp_files;
How do I find used/free space in a TEMPORARY tablespace? (for DBA )
Unlike normal tablespaces, true temporary
tablespace information is not listed in DBA_FREE_SPACE. Instead use the
V$TEMP_SPACE_HEADER view:
SELECT tablespace_name, SUM (bytes used), SUM (bytes free)
FROM V$temp_space_header
GROUP BY tablespace_name;
What is a profile ?
Each database user is assigned a Profile that specifies limitations on various system resources available to the user.
How will you enforce security using stored procedures?
Don't grant user access directly to
tables within the application. Instead grant the ability to access the
procedures that access the tables. When procedure executed it will
execute the privilege of procedures owner. Users cannot access tables
except via the procedure.
How can one see who is using a temporary segment? (for DBA )
For every user using temporary space, there is an entry in SYS.V$_LOCK with type 'TS'.
All temporary segments are named 'ffff.bbbb' where 'ffff' is the
file it is in and 'bbbb' is first block of the segment. If your
temporary tablespace is set to TEMPORARY, all sorts are done in one
large temporary segment. For usage stats, see SYS.V_$SORT_SEGMENT
From Oracle 8.0, one can just query SYS.v$sort_usage. Look at these examples:
select s.username, u."USER", u.tablespace, u.contents, u.extents, u.blocks
from sys.v_$session s, sys.v_$sort_usage u
where s.addr = u.session_addr
/
select s.osuser, s.process, s.username, s.serial#,
Sum (u.blocks)*vp.value/1024 sort_size
from sys.v_$session s, sys.v_$sort_usage u, sys.v_$parameter VP
where s.saddr = u.session_addr
and vp.name = 'db_block_size'
and s.osuser like '&1'
group by s.osuser, s.process, s.username, s.serial#, vp.value
/
How does one get the view definition of fixed views/tables?
Query v$fixed_view_definition. Example: SELECT * FROM v$fixed_view_definition WHERE view_name='V$SESSION';
What are the dictionary tables used to monitor a database spaces ?
DBA_FREE_SPACE
DBA_SEGMENTS
DBA_DATA_FILES.
How can we specify the Archived log file name format and destination?
By setting the following values in
init.ora file. LOG_ARCHIVE_FORMAT = arch %S/s/T/tarc (%S - Log sequence
number and is zero left paded, %s - Log sequence number not padded. %T -
Thread number lef-zero-paded and %t - Thread number not padded). The
file name created is arch 0001 are if %S is used. LOG_ARCHIVE_DEST =
path.
What is user Account in Oracle database?
An user account is not a physical
structure in Database but it is having important relationship to the
objects in the database and will be having certain privileges.
When will the data in the snapshot log be used?
We must be able to create a after row
trigger on table (i.e., it should be not be already available) After
giving table privileges. We cannot specify snapshot log name because
oracle uses the name of the master table in the name of the database
objects that support its snapshot log. The master table name should be
less than or equal to 23 characters. (The table name created will be
MLOGS_tablename, and trigger name will be TLOGS name).
What dynamic data replication?
Updating or Inserting records in remote
database through database triggers. It may fail if remote database is
having any problem.
What is Two-Phase Commit ?
Two-phase commit is mechanism that
guarantees a distributed transaction either commits on all involved
nodes or rolls back on all involved nodes to maintain data consistency
across the global distributed database. It has two phase, a Prepare
Phase and a Commit Phase.
How can you Enforce Referential Integrity in snapshots ?
Time the references to occur when master
tables are not in use. Peform the reference the manually immdiately
locking the master tables. We can join tables in snopshots by creating a
complex snapshots that will based on the master tables.
What is a SQL * NET?
SQL *NET is ORACLE's mechanism for
interfacing with the communication protocols used by the networks that
facilitate distributed processing and distributed databases. It is used
in Clint-Server and Server-Server communications.
What is a SNAPSHOT ?
Snapshots are read-only copies of a
master table located on a remote node which is periodically refreshed to
reflect changes made to the master table.
What is the mechanism provided by ORACLE for table replication ?
Snapshots and SNAPSHOT LOGs
What is snapshots?
Snapshot is an object used to dynamically
replicate data between distribute database at specified time intervals.
In ver 7.0 they are read only.
What are the various type of snapshots?
Simple and Complex.
Describe two phases of Two-phase commit ?
Prepare phase - The global coordinator
(initiating node) ask a participants to prepare (to promise to commit or
rollback the transaction, even if there is a failure) Commit - Phase -
If all participants respond to the coordinator that they are prepared,
the coordinator asks all nodes to commit the transaction, if all
participants cannot prepare, the coordinator asks all nodes to roll back
the transaction.
What is snapshot log ?
It is a table that maintains a record of
modifications to the master table in a snapshot. It is stored in the
same database as master table and is only available for simple
snapshots. It should be created before creating snapshots.
What are the benefits of distributed options in databases?
Database on other servers can be updated and those transactions can be grouped together with others in a logical unit.
Database uses a two phase commit.
What are the options available to refresh snapshots ?
COMPLETE - Tables are completely regenerated using the snapshots query and the master tables every time the snapshot referenced.
FAST - If simple snapshot used then a snapshot log can be used to send the changes to the snapshot tables.
FORCE - Default value. If possible it performs a FAST refresh; Otherwise it will perform a complete refresh.
What is a SNAPSHOT LOG ?
A snapshot log is a table in the master
database that is associated with the master table. ORACLE uses a
snapshot log to track the rows that have been updated in the master
table. Snapshot logs are used in updating the snapshots based on the
master table.
What is Distributed database ?
A distributed database is a network of
databases managed by multiple database servers that appears to a user as
single logical database. The data of all databases in the distributed
database can be simultaneously accessed and modified.
How can we reduce the network traffic?
- Replication of data in distributed environment.
- Using snapshots to replicate data.
- Using remote procedure calls.
Differentiate simple and complex, snapshots ?
- A simple snapshot is based on a query
that does not contains GROUP BY clauses, CONNECT BY clauses, JOINs,
sub-query or snashot of operations.
- A complex snapshots contain atleast any one of the above.
What are the Built-ins used for sending Parameters to forms?
You can pass parameter values to a form when an application executes the call_form, New_form, Open_form or Run_product.
Can you have more than one content canvas view attached with a window?
Yes. Each window you create must have
atleast one content canvas view assigned to it. You can also create a
window that has manipulated content canvas view. At run time only one of
the content canvas views assign to a window is displayed at a time.
Is the After report trigger fired if the report execution fails?
Yes.
Does a Before form trigger fire when the parameter form is suppressed?
Yes.
What is SGA?
The System Global Area in an Oracle
database is the area in memory to facilitate the transfer of information
between users. It holds the most recently requested structural
information between users. It holds the most recently requested
structural information about the database. The structure is database
buffers, dictionary cache, redo log buffer and shared pool area.
What is a shared pool?
The data dictionary cache is stored in an
area in SGA called the shared pool. This will allow sharing of parsed
SQL statements among concurrent users.
What is mean by Program Global Area (PGA)?
It is area in memory that is used by a single Oracle user process.
What is a data segment?
Data segment are the physical areas within a database block in which the data associated with tables and clusters are stored.
What are the factors causing the reparsing of SQL statements in SGA?
Due to insufficient shared pool size.
Monitor the ratio of the reloads takes place while executing SQL
statements. If the ratio is greater than 1 then increase the
SHARED_POOL_SIZE.
What are clusters?
Clusters are groups of one or more tables physically stores together to share common columns and are often used together.
What is cluster key?
The related columns of the tables in a cluster are called the cluster key.
Do a view contain data?
Views do not contain or store data.
What is user Account in Oracle database?
A user account is not a physical
structure in database but it is having important relationship to the
objects in the database and will be having certain privileges.
How will you enforce security using stored procedures?
Don't grant user access directly to
tables within the application. Instead grant the ability to access the
procedures that access the tables. When procedure executed it will
execute the privilege of procedures owner. Users cannot access tables
except via the procedure.
What are the dictionary tables used to monitor a database space?
DBA_FREE_SPACE
DBA_SEGMENTS
DBA_DATA_FILES.
Can a property clause itself be based on a property clause?
Yes
If a parameter is used in a
query without being previously defined, what diff. exist between. report
2.0 and 2.5 when the query is applied?
While both reports 2.0 and 2.5 create the parameter, report 2.5 gives a message that a bind parameter has been created.
What are the sql clauses supported in the link property sheet?
Where start with having.
What is trigger associated with the timer?
When-timer-expired.
What are the trigger associated with image items?
When-image-activated fires when the
operators double clicks on an image itemwhen-image-pressed fires when an
operator clicks or double clicks on an image item
What are the different windows events activated at runtimes?
When_window_activated
When_window_closed
When_window_deactivated
When_window_resized
Within this triggers, you can examine the built in system variable
system. event_window to determine the name of the window for which the
trigger fired.
When do you use data parameter type?
When the value of a data parameter being
passed to a called product is always the name of the record group
defined in the current form. Data parameters are used to pass data to
products invoked with the run_product built-in subprogram.
What is difference between open_form and call_form?
when one form invokes another form by
executing open_form the first form remains displayed, and operators can
navigate between the forms as desired. when one form invokes another
form by executing call_form, the called form is modal with respect to
the calling form. That is, any windows that belong to the calling form
are disabled, and operators cannot navigate to them until they first
exit the called form.
What is new_form built-in?
When one form invokes another form by
executing new_form oracle form exits the first form and releases its
memory before loading the new form calling new form completely replace
the first with the second. If there are changes pending in the first
form, the operator will be prompted to save them before the new form is
loaded.
What is the "LOV of Validation" Property of an item? What is the use of it?
When LOV for Validation is set to True,
Oracle Forms compares the current value of the text item to the values
in the first column displayed in the LOV. Whenever the validation event
occurs. If the value in the text item matches one of the values in the
first column of the LOV, validation succeeds, the LOV is not displayed,
and processing continues normally. If the value in the text item does
not match one of the values in the first column of the LOV, Oracle Forms
displays the LOV and uses the text item value as the search criteria to
automatically reduce the list.
What is the diff. when Flex mode is mode on and when it is off?
When flex mode is on, reports automatically resizes the parent when the child is resized.
What is the diff. when confine mode is on and when it is off?
When confine mode is on, an object cannot be moved outside its parent in the layout.
What are visual attributes?
Visual attributes are the font, color,
pattern proprieties that you set for form and menu objects that appear
in your application interface.
Which of the two views should objects according to possession?
view by structure.
What are the two types of views available in the object navigator(specific to report 2.5)?
View by structure and view by type .
What are the vbx controls?
Vbx control provide a simple method of
building and enhancing user interfaces. The controls can use to obtain
user inputs and display program outputs.vbx control where originally
develop as extensions for the ms visual basic environments and include
such items as sliders, rides and knobs.
What is the use of transactional triggers?
Using transactional triggers we can control or modify the default functionality of the oracle forms.
How do you create a new session while open a new form?
Using open_form built-in setting the
session option Ex. Open_form('Stocks ',active, session). when invoke the
multiple forms with open form and call_form in the same application,
state whether the following are true/False
What are the ways to monitor the performance of the report?
Use reports profile executable statement. Use SQL trace facility.
If two groups are not linked in the data model editor, What is the hierarchy between them?
Two group that is above are the left most rank higher than the group that is to right or below it.
An open form can not be execute the call_form procedure if you chain of called forms has been initiated by another open form?
True
Explain about horizontal, Vertical tool bar canvas views?
Tool bar canvas views are used to create
tool bars for individual windows. Horizontal tool bars are display at
the top of a window, just under its menu bar. Vertical Tool bars are
displayed along the left side of a window
What is the purpose of the product order option in the column property sheet?
To specify the order of individual group evaluation in a cross products.
What is the use of image_zoom built-in?
To manipulate images in image items.
How do you reference a parameter indirectly?
To indirectly reference a parameter use
the NAME IN, COPY 'built-ins to indirectly set and reference the
parameters value' Example name_in ('capital parameter my param'), Copy
('SURESH','Parameter my_param')
What is a timer?(Forms and Reports)
Timer is an "internal time clock" that you can programmatically create to perform an action each time the times.
What are the two phases of block coordination?
There are two phases of block
coordination: the clear phase and the population phase. During, the
clear phase, Oracle Forms navigates internally to the detail block and
flushes the obsolete detail records. During the population phase, Oracle
Forms issues a SELECT statement to repopulate the detail block with
detail records associated with the new master record. These operations
are accomplished through the execution of triggers.
What are Most Common types of Complex master-detail relationships?
There are three most common types of complex master-detail relationships:
master with dependent details
master with independent details
detail with two masters
What is a text list?
The text list style list item appears as a
rectangular box which displays the fixed number of values. When the
text list contains values that can not be displayed, a vertical scroll
bar appears, allowing the operator to view and select undisplayed
values.
What is term?
The term is terminal definition file that describes the terminal form which you are using r20run.
What is use of term?
The term file which key is correspond to which oracle report functions.
What is pop list?
The pop list style list item appears
initially as a single field (similar to a text item field). When the
operator selects the list icon, a list of available choices appears.
What is the maximum no of chars the parameter can store?
The maximum no of chars the parameter can
store is only valid for char parameters, which can be upto 64K. No
parameters default to 23Bytes and Date parameter default to 7Bytes.
What are the default extensions of the files created by library module?
The default file extensions indicate the library module type and storage format .pll - pl/sql library module binary
What are the Coordination Properties in a Master-Detail relationship?
The coordination properties are
Deferred
Auto-Query
These Properties determine when the population phase of block
coordination should occur.
How do you display console on a window ?
The console includes the status line and
message line, and is displayed at the bottom of the window to which it
is assigned.To specify that the console should be displayed, set the
console window form property to the name of any window in the form. To
include the console, set console window to Null.
What are the different Parameter types?
Text ParametersData Parameters
State any three mouse events system variables?
System.mouse_button_pressedSystem.mouse_button_shift
What are the types of calculated columns available?
Summary, Formula, Placeholder column.
Explain about stacked canvas views?
Stacked canvas view is displayed in a
window on top of, or "stacked" on the content canvas view assigned to
that same window. Stacked canvas views obscure some part of the
underlying content canvas view, and or often shown and hidden
programmatically.
How does one do off-line database backups? (for DBA )
Shut down the database from sqlplus or
server manager. Backup all files to secondary storage (eg. tapes).
Ensure that you backup all data files, all control files and all log
files. When completed, restart your database.
Do the following queries to get a list of all files that needs to be backed up:
select name from sys.v_$datafile;
select member from sys.v_$logfile;
select name from sys.v_$controlfile;
Sometimes Oracle takes forever to shutdown with the "immediate"
option. As workaround to this problem, shutdown using these commands:
alter system checkpoint;
shutdown abort
startup restrict
shutdown immediate
Note that if you database is in ARCHIVELOG mode, one can still use
archived log files to roll forward from an off-line backup. If you
cannot take your database down for a cold (off-line) backup at a
convenient time, switch your database into ARCHIVELOG mode and perform
hot (on-line) backups.
What is the difference between SHOW_EDITOR and EDIT_TEXTITEM?
Show editor is the generic built-in which
accepts any editor name and takes some input string and returns
modified output string. Whereas the edit_textitem built-in needs the
input focus to be in the text item before the built-in is executed.
What are the built-ins that are used to Attach an LOV programmatically to an item?
set_item_property
get_item_property
(by setting the LOV_NAME property)
How does one do on-line database backups? (for DBA )
Each tablespace that needs to be
backed-up must be switched into backup mode before copying the files out
to secondary storage (tapes). Look at this simple example.
ALTER TABLESPACE xyz BEGIN BACKUP;
! cp xyfFile1 /backupDir/
ALTER TABLESPACE xyz END BACKUP;
It is better to backup tablespace for tablespace than to put all
tablespaces in backup mode. Backing them up separately incurs less
overhead. When done, remember to backup your control files. Look at this
example:
ALTER SYSTEM SWITCH LOGFILE; -- Force log switch to update control file headers
ALTER DATABASE BACKUP CONTROLFILE TO '/backupDir/control.dbf';
NOTE: Do not run on-line backups during peak processing periods.
Oracle will write complete database blocks instead of the normal deltas
to redo log files while in backup mode. This will lead to excessive
database archiving and even database freezes.
How does one backup a database using RMAN? (for DBA )
The biggest advantage of RMAN is that it
only backup used space in the database. Rman doesn't put tablespaces in
backup mode, saving on redo generation overhead. RMAN will re-read
database blocks until it gets a consistent image of it. Look at this
simple backup example.
rman target sys/*** nocatalog
run {
allocate channel t1 type disk;
backup
format '/app/oracle/db_backup/%d_t%t_s%s_p%p'
( database );
release channel t1;
}
Example RMAN restore:
rman target sys/*** nocatalog
run {
allocate channel t1 type disk;
# set until time 'Aug 07 2000 :51';
restore tablespace users;
recover tablespace users;
release channel t1;
}
The examples above are extremely simplistic and only useful for
illustrating basic concepts. By default Oracle uses the database
controlfiles to store information about backups. Normally one would
rather setup a RMAN catalog database to store RMAN metadata in. Read the
Oracle Backup and Recovery Guide before implementing any RMAN backups.
Note: RMAN cannot write image copies directly to tape. One needs to
use a third-party media manager that integrates with RMAN to backup
directly to tape. Alternatively one can backup to disk and then manually
copy the backups to tape.
What are the different file extensions that are created by oracle reports?
Rep file and Rdf file.
What is strip sources generate options?
Removes the source code from the library
file and generates a library files that contains only pcode. The
resulting file can be used for final deployment, but can not be
subsequently edited in the designer.ex. f45gen module=old_lib.pll
userid=scott/tiger strip_source YES output_file
How does one put a database into ARCHIVELOG mode? (for DBA )
The main reason for running in archivelog
mode is that one can provide 24-hour availability and guarantee
complete data recoverability. It is also necessary to enable ARCHIVELOG
mode before one can start to use on-line database backups. To enable
ARCHIVELOG mode, simply change your database startup command script, and
bounce the database:
SQLPLUS> connect sys as sysdba
SQLPLUS> startup mount exclusive;
SQLPLUS> alter database archivelog;
SQLPLUS> archive log start;
SQLPLUS> alter database open;
NOTE1: Remember to take a baseline database backup right after
enabling archivelog mode. Without it one would not be able to recover.
Also, implement an archivelog backup to prevent the archive log
directory from filling-up.
NOTE2: ARCHIVELOG mode was introduced with Oracle V6, and is
essential for database point-in-time recovery. Archiving can be used in
combination with on-line and off-line database backups.
NOTE3: You may want to set the following INIT.ORA parameters when
enabling ARCHIVELOG mode: log_archive_start=TRUE, log_archive_dest=...
and log_archive_format=...
NOTE4: You can change the archive log destination of a database
on-line with the ARCHIVE LOG START TO 'directory'; statement. This
statement is often used to switch archiving between a set of
directories.
NOTE5: When running Oracle Real Application Server (RAC), you need
to shut down all nodes before changing the database to ARCHIVELOG mode.
What is the basic data structure that is required for creating an LOV?
Record Group.
How does one backup archived log files? (for DBA )
One can backup archived log files using
RMAN or any operating system backup utility. Remember to delete files
after backing them up to prevent the archive log directory from filling
up. If the archive log directory becomes full, your database will hang!
Look at this simple RMAN backup script:
RMAN> run {
2> allocate channel dev1 type disk;
3> backup
4> format '/app/oracle/arch_backup/log_t%t_s%s_p%p'
5> (archivelog all delete input);
6> release channel dev1;
7> }
Does Oracle write to data files in begin/hot backup mode? (for DBA )
Oracle will stop updating file headers,
but will continue to write data to the database files even if a
tablespace is in backup mode.
In backup mode, Oracle will write out complete changed blocks to
the redo log files. Normally only deltas (changes) are logged to the
redo logs. This is done to enable reconstruction of a block if only half
of it was backed up (split blocks). Because of this, one should notice
increased log activity and archiving during on-line backups.
What is the Maximum allowed length of Record group Column?
Record group column names cannot exceed 30 characters.
Which parameter can be used to set read level consistency across multiple queries?
Read only
What are the different types of Record Groups?
Query Record Groups
NonQuery Record Groups
State Record Groups
From which designation is it preferred to send the output to the printed?
Previewer
What are difference between post database commit and post-form commit?
Post-form commit fires once during the
post and commit transactions process, after the database commit occurs.
The post-form-commit trigger fires after inserts, updates and deletes
have been posted to the database but before the transactions have been
finalized in the issuing the command. The post-database-commit trigger
fires after oracle forms issues the commit to finalized transactions.
What are the different display styles of list items?
Pop_listText_listCombo box
Which of the above methods is the faster method?
performing the calculation in the query is faster.
With which function of summary item is the compute at options required?
percentage of total functions.
What are parameters?
Parameters provide a simple mechanism for
defining and setting the valuesof inputs that are required by a form at
startup. Form parameters are variables of type char,number,date that
you define at design time.
What are the three types of user exits available ?
Oracle Precompiler exits, Oracle call interface, NonOracle user exits.
How many windows in a form can have console?
Only one window in a form can display the console, and you cannot change the console assignment at runtime.
What is an administrative (privileged) user? (for DBA )
Oracle DBAs and operators typically use
administrative accounts to manage the database and database instance. An
administrative account is a user that is granted SYSOPER or SYSDBA
privileges. SYSDBA and SYSOPER allow access to a database instance even
if it is not running. Control of these privileges is managed outside of
the database via password files and special operating system groups.
This password file is created with the orapwd utility.
What are the two repeating frame always associated with matrix object?
One down repeating frame below one across repeating frame.
What are the master-detail triggers?
On-Check_delete_masterOn_clear_detailsOn_populate_details
How does one connect to an administrative user? (for DBA )
If an administrative user belongs to the
"dba" group on Unix, or the "ORA_DBA" (ORA_sid_DBA) group on NT, he/she
can connect like this:
connect / as sysdba
No password is required. This is equivalent to the desupported "connect internal" method.
A password is required for "non-secure" administrative access.
These passwords are stored in password files. Remote connections via
Net8 are classified as non-secure. Look at this example:
connect sys/password as sysdba
How does one create a password file? (for DBA )
The Oracle Password File
($ORACLE_HOME/dbs/orapw or orapwSID) stores passwords for users with
administrative privileges. One needs to create a password files before
remote administrators (like OEM) will be allowed to connect.
Follow this procedure to create a new password file:
. Log in as the Oracle software owner
. Runcommand: orapwd file=$ORACLE_HOME/dbs/orapw$ORACLE_SID password=mypasswd
. Shutdown the database (SQLPLUS> SHUTDOWN IMMEDIATE)
. Edit the INIT.ORA file and ensure REMOTE_LOGIN_PASSWORDFILE=exclusive is set.
. Startup the database (SQLPLUS> STARTUP)
NOTE: The orapwd utility presents a security risk in that it
receives a password from the command line. This password is visible in
the process table of many systems. Administrators needs to be aware of
this!
Is it possible to modify an external query in a report which contains it?
No.
Does a grouping done for objects in the layout editor affect the grouping done in the data model editor?
No.
How does one add users to a password file? (for DBA )
One can select from the
SYS.V_$PWFILE_USERS view to see which users are listed in the password
file. New users can be added to the password file by granting them
SYSDBA or SYSOPER privileges, or by using the orapwd utility. GRANT
SYSDBA TO scott;
If a break order is set on a column would it affect columns which are under the column?
No
Why are OPS$ accounts a security risk in a client/server environment? (for DBA)
If you allow people to log in with OPS$
accounts from Windows Workstations, you cannot be sure who they really
are. With terminals, you can rely on operating system passwords, with
Windows, you cannot.
If you set REMOTE_OS_AUTHENT=TRUE in your init.ora file, Oracle
assumes that the remote OS has authenticated the user. If
REMOTE_OS_AUTHENT is set to FALSE (recommended), remote users will be
unable to connect without a password. IDENTIFIED EXTERNALLY will only be
in effect from the local host. Also, if you are using "OPS$" as your
prefix, you will be able to log on locally with or without a password,
regardless of whether you have identified your ID with a password or
defined it to be IDENTIFIED EXTERNALLY.
Do user parameters appear in the data modal editor in 2.5?
No
Can you pass data parameters to forms?
No
Is it possible to link two groups inside a cross products after the cross products group has been created?
no
What are the different modals of windows?
Modalless windows
Modal windows
What are modal windows?
Modal windows are usually used as
dialogs, and have restricted functionality compared to modelless
windows. On some platforms for example operators cannot resize, scroll
or iconify a modal window.
What are the different default triggers created when Master Deletes Property is set to Non-isolated?
Master Deletes Property Resulting Triggers
----------------------------------------------------
Non-Isolated(the default) On-Check-Delete-Master
On-Clear-Details
On-Populate-Details
What are the different default triggers created when Master Deletes Property is set to isolated?
Master Deletes Property Resulting Triggers
---------------------------------------------------
Isolated On-Clear-Details
On-Populate-Details
What are the different default triggers created when Master Deletes Property is set to Cascade?
Master Deletes Property Resulting Triggers
---------------------------------------------------
Cascading On-Clear-Details
On-Populate-Details
Pre-delete
What is the diff. bet. setting up of parameters in reports 2.0 reports2.5?
LOVs can be attached to parameters in the reports 2.5 parameter form.
What are the difference between lov & list item?
Lov is a property where as list item is an item. A list item can have only one column, lov can have one or more columns.
What is the advantage of the library?
Libraries provide a convenient means
of storing client-side program units and sharing them among multiple
applications. Once you create a library, you can attach it to any other
form, menu, or library modules. When you can call library program units
from triggers menu items commands and user named routine, you write in
the modules to which you have attach the library. When a library
attaches another library, program units in the first library can
reference program units in the attached library. Library support dynamic
loading-that is library program units are loaded into an application
only when needed. This can significantly reduce the run-time memory
requirements of applications.
What is lexical reference? How can it be created?
Lexical reference is place_holder for
text that can be embedded in a sql statements. A lexical reference can
be created using & before the column or parameter name.
What is system.coordination_operation?
It represents the coordination causing event that occur on the master block in master-detail relation.
What is synchronize?
It is a terminal screen with the
internal state of the form. It updates the screen display to reflect the
information that oracle forms has in its internal representation of the
screen.
What use of command line parameter cmd file?
It is a command line argument that allows you to specify a file that contain a set of arguments for r20run.
What is a Text_io Package?
It allows you to read and write information to a file in the file system.
What is forms_DDL?
Issues dynamic Sql statements at run time, including server side pl/SQl and DDL
How is link tool operation different bet. reports 2 & 2.5?
In Reports 2.0 the link tool has to be
selected and then two fields to be linked are selected and the link is
automatically created. In 2.5 the first field is selected and the link
tool is then used to link the first field to the second field.
What are the different styles of activation of ole Objects?
In place activationExternal activation
How do you reference a Parameter?
In Pl/Sql, You can reference and set the
values of form parameters using bind variables syntax. Ex. PARAMETER
name = '' or :block.item = PARAMETER Parameter name
What is the difference between object embedding & linking in Oracle forms?
In Oracle forms, Embedded objects become
part of the form module, and linked objects are references from a form
module to a linked source file.
Name of the functions used to get/set canvas properties?
Get_view_property, Set_view_property
What are the built-ins that are used for setting the LOV properties at runtime?
get_lov_property
set_lov_property
What are the built-ins used for processing rows?
Get_group_row_count(function)
Get_group_selection_count(function)
Get_group_selection(function)
Reset_group_selection(procedure)
Set_group_selection(procedure)
Unset_group_selection(procedure)
What are built-ins used for Processing rows?
GET_GROUP_ROW_COUNT(function)
GET_GROUP_SELECTION_COUNT(function)
GET_GROUP_SELECTION(function)
RESET_GROUP_SELECTION(procedure)
SET_GROUP_SELECTION(procedure)
UNSET_GROUP_SELECTION(procedure)
What are the built-in used for getting cell values?
Get_group_char_cell(function)
Get_groupcell(function)
Get_group_number_cell(function)
What are the built-ins used for Getting cell values?
GET_GROUP_CHAR_CELL (function)
GET_GROUPCELL(function)
GET_GROUP_NUMBET_CELL(function)
Atleast how many set of data must a data model have before a data model can be base on it?
Four
To execute row from being displayed that still use column in the row which property can be used?
Format trigger.
What are different types of modules available in oracle form?
Form module - a collection of objects and
code routines Menu modules - a collection of menus and menu item
commands that together make up an application menu library module - a
collection of user named procedures, functions and packages that can be
called from other modules in the application
What is the remove on exit property?
For a modelless window, it determines
whether oracle forms hides the window automatically when the operators
navigates to an item in the another window.
What is WHEN-Database-record trigger?
Fires when oracle forms first marks a
record as an insert or an update. The trigger fires as soon as oracle
forms determines through validation that the record should be processed
by the next post or commit as an insert or update. c generally occurs
only when the operators modifies the first item in the record, and after
the operator attempts to navigate out of the item.
What is a difference between pre-select and pre-query?
Fires during the execute query and count
query processing after oracle forms constructs the select statement to
be issued, but before the statement is actually issued. The pre-query
trigger fires just before oracle forms issues the select statement to
the database after the operator as define the example records by
entering the query criteria in enter query mode.Pre-query trigger fires
before pre-select trigger.
What are built-ins associated with timers?
find_timercreate_timerdelete_timer
What are the built-ins used for finding object ID functions?
Find_group(function)
Find_column(function)
What are the built-ins used for finding Object ID function?
FIND_GROUP(function)
FIND_COLUMN(function)
Any attempt to navigate programmatically to disabled form in a call_form stack is allowed?
False
Use the Add_group_row procedure to add a row to a static record group 1. true or false?
False
What third party tools can be used with Oracle EBU/ RMAN? (for DBA)
The following Media Management
Software Vendors have integrated their media management software
packages with Oracle Recovery Manager and Oracle7 Enterprise Backup
Utility. The Media Management Vendors will provide first line technical
support for the integrated backup/recover solutions.
Veritas NetBackup
EMC Data Manager (EDM)
HP OMNIBack II
IBM's Tivoli Storage Manager - formerly ADSM
Legato Networker
ManageIT Backup and Recovery
Sterling Software's SAMS:Alexandria - formerly from Spectralogic
Sun Solstice Backup
Why and when should one tune? (for DBA)
One of the biggest responsibilities of a
DBA is to ensure that the Oracle database is tuned properly. The Oracle
RDBMS is highly tunable and allows the database to be monitored and
adjusted to increase its performance. One should do performance tuning
for the following reasons:
The speed of computing might be wasting valuable human time (users
waiting for response); Enable your system to keep-up with the speed
business is conducted; and Optimize hardware usage to save money
(companies are spending millions on hardware). Although this FAQ is not
overly concerned with hardware issues, one needs to remember than you
cannot tune a Buick into a Ferrari.
How can a break order be
created on a column in an existing group? What are the various sub
events a mouse double click event involves?
By dragging the column outside the group.
What is the use of place holder column? What are the various sub events a mouse double click event involves?
A placeholder column is used to hold
calculated values at a specified place rather than allowing is to appear
in the actual row where it has to appear.
What is the use of hidden column? What are the various sub events a mouse double click event involves?
A hidden column is used to when a column has to embed into boilerplate text.
What database aspects should be monitored? (for DBA)
One should implement a monitoring system
to constantly monitor the following aspects of a database. Writing
custom scripts, implementing Oracle's Enterprise Manager, or buying a
third-party monitoring product can achieve this. If an alarm is
triggered, the system should automatically notify the DBA (e-mail, page,
etc.) to take appropriate action.
Infrastructure availability:
. Is the database up and responding to requests
. Are the listeners up and responding to requests
. Are the Oracle Names and LDAP Servers up and responding to requests
. Are the Web Listeners up and responding to requests
Things that can cause service outages:
. Is the archive log destination filling up?
. Objects getting close to their max extents
. User and process limits reached
Things that can cause bad performance:
See question "What tuning indicators can one use?".
Where should the tuning effort be directed? (for DBA)
Consider the following areas for tuning.
The order in which steps are listed needs to be maintained to prevent
tuning side effects. For example, it is no good increasing the buffer
cache if you can reduce I/O by rewriting a SQL statement. Database
Design (if it's not too late):
Poor system performance usually results from a poor database
design. One should generally normalize to the 3NF. Selective
denormalization can provide valuable performance improvements. When
designing, always keep the "data access path" in mind. Also look at
proper data partitioning, data replication, aggregation tables for
decision support systems, etc.
Application Tuning:
Experience showed that approximately 80% of all Oracle system
performance problems are resolved by coding optimal SQL. Also consider
proper scheduling of batch tasks after peak working hours.
Memory Tuning:
Properly size your database buffers (shared pool, buffer cache, log
buffer, etc) by looking at your buffer hit ratios. Pin large objects
into memory to prevent frequent reloads.
Disk I/O Tuning:
Database files needs to be properly sized and placed to provide
maximum disk subsystem throughput. Also look for frequent disk sorts,
full table scans, missing indexes, row chaining, data fragmentation, etc
Eliminate Database Contention:
Study database locks, latches and wait events carefully and eliminate where possible. Tune the Operating System:
Monitor and tune operating system CPU, I/O and memory utilization.
For more information, read the related Oracle FAQ dealing with your
specific operating system.
What are the various sub
events a mouse double click event involves? What are the various sub
events a mouse double click event involves?
Double clicking the mouse consists of the mouse down, mouse up, mouse click, mouse down & mouse up events.
What are the default
parameter that appear at run time in the parameter screen? What are the
various sub events a mouse double click event involves?
Destype and Desname.
What are the built-ins used for Creating and deleting groups?
CREATE-GROUP (function)
CREATE_GROUP_FROM_QUERY(function)
DELETE_GROUP(procedure)
What are different types of canvas views?
Content canvas views
Stacked canvas views
Horizontal toolbar
vertical toolbar.
What are the different types of Delete details we can establish in Master-Details?
Cascade
Isolate
Non-isolate
What is relation between the window and canvas views?
Canvas views are the back ground objects
on which you place the interface items (Text items), check boxes, radio
groups etc.,) and boilerplate objects (boxes, lines, images etc.,) that
operators interact with us they run your form . Each canvas views
displayed in a window.
What is a User_exit?
Calls the user exit named in the
user_exit_string. Invokes a 3Gl program by name which has been properly
linked into your current oracle forms executable.
How is it possible to select generate a select set for the query in the query property sheet?
By using the tables/columns button and then specifying the table and the column names.
How can values be passed bet. precompiler exits & Oracle call interface?
By using the statement EXECIAFGET & EXECIAFPUT.
How can a square be drawn in the layout editor of the report writer?
By using the rectangle tool while pressing the (Constraint) key.
How can a text file be attached to a report while creating in the report writer?
By using the link file property in the layout boiler plate property sheet.
How can I message to passed to the user from reports?
By using SRW.MESSAGE function.
Does one need to drop/ truncate objects before importing? (for DBA)
Before one import rows into already
populated tables, one needs to truncate or drop these tables to get rid
of the old data. If not, the new data will be appended to the existing
tables. One must always DROP existing Sequences before re-importing. If
the sequences are not dropped, they will generate numbers inconsistent
with the rest of the database. Note: It is also advisable to drop
indexes before importing to speed up the import process. Indexes can
easily be recreated after the data was successfully imported.
How can a button be used in a report to give a drill down facility?
By setting the action associated with button to Execute pl/sql option and using the SRW.Run_report function.
Can one import/export between different versions of Oracle? (for DBA)
Different versions of the import utility
is upwards compatible. This means that one can take an export file
created from an old export version, and import it using a later version
of the import utility. This is quite an effective way of upgrading a
database from one release of Oracle to the next.
Oracle also ships some previous catexpX.sql scripts that can be
executed as user SYS enabling older imp/exp versions to work (for
backwards compatibility). For example, one can run
$ORACLE_HOME/rdbms/admin/catexp7.sql on an Oracle 8 database to allow
the Oracle 7.3 exp/imp utilities to run against an Oracle 8 database.
What are different types of images?
Boiler plate imagesImage Items
Can one export to multiple files?/ Can one beat the Unix 2 Gig limit? (for DBA)
From Oracle8i, the export utility
supports multiple output files. This feature enables large exports to be
divided into files whose sizes will not exceed any operating system
limits (FILESIZE= parameter). When importing from multi-file export you
must provide the same filenames in the same sequence in the FILE=
parameter. Look at this example:
exp SCOTT/TIGER FILE=D:\F1.dmp,E:\F2.dmp FILESIZE=10m LOG=scott.log
Use the following technique if you use an Oracle version prior to 8i:
Create a compressed export on the fly. Depending on the type of
data, you probably can export up to 10 gigabytes to a single file. This
example uses gzip. It offers the best compression I know of, but you can
also substitute it with zip, compress or whatever.
# create a named pipe
mknod exp.pipe p
# read the pipe - output to zip file in the background
gzip < exp.pipe > scott.exp.gz &
# feed the pipe
exp userid=scott/tiger file=exp.pipe ...
What is bind reference and how can it be created?
Bind reference are used to replace the
single value in sql, pl/sql statements a bind reference can be created
using a (:) before a column or a parameter name.
How can one improve Import/ Export performance? (for DBA)
EXPORT:
. Set the BUFFER parameter to a high value (e.g. 2M)
. Set the RECORDLENGTH parameter to a high value (e.g. 64K)
. Stop unnecessary applications to free-up resources for your job.
. If you run multiple export sessions, ensure they write to different physical disks.
. DO NOT export to an NFS mounted filesystem. It will take forever.
IMPORT:
. Create an indexfile so that you can create indexes AFTER you have
imported data. Do this by setting INDEXFILE to a filename and then
import. No data will be imported but a file containing index definitions
will be created. You must edit this file afterwards and supply the
passwords for the schemas on all CONNECT statements.
. Place the file to be imported on a separate physical disk from the oracle data files
. Increase DB_CACHE_SIZE (DB_BLOCK_BUFFERS prior to 9i) considerably in the init$SID.ora file
. Set the LOG_BUFFER to a big value and restart oracle.
. Stop redo log archiving if it is running (ALTER DATABASE NOARCHIVELOG;)
. Create a BIG tablespace with a BIG rollback segment inside. Set
all other rollback segments offline (except the SYSTEM rollback segment
of course). The rollback segment must be as big as your biggest table (I
think?)
. Use COMMIT=N in the import parameter file if you can afford it
. Use ANALYZE=N in the import parameter file to avoid time consuming ANALYZE statements
. Remember to run the indexfile previously created
Give the sequence of execution of the various report triggers?
Before form , After form , Before report, Between page, After report.
What are the common Import/ Export problems? (for DBA )
ORA-00001: Unique constraint (...)
violated - You are importing duplicate rows. Use IGNORE=NO to skip
tables that already exist (imp will give an error if the object is
re-created).
ORA-01555: Snapshot too old - Ask your users to STOP working while you are exporting or use parameter CONSISTENT=NO
ORA-01562: Failed to extend rollback segment - Create bigger rollback segments or set parameter COMMIT=Y while importing
IMP-00015: Statement failed ... object already exists... - Use the
IGNORE=Y import parameter to ignore these errors, but be careful as you
might end up with duplicate rows.
Why is it preferable to create a fewer no. of queries in the data model?
Because for each query, report has to open a separate cursor and has to rebind, execute and fetch data.
Where is the external query executed at the client or the server?
At the server.
Where is a procedure return in an external pl/sql library executed at the client or at the server?
At the client.
What is coordination Event?
Any event that makes a different record in the master block the current record is a coordination causing event.
What is the difference between OLE Server & Ole Container?
An Ole server application creates ole
Objects that are embedded or linked in ole Containers ex. Ole servers
are ms_word & ms_excel. OLE containers provide a place to store,
display and manipulate objects that are created by ole server
applications. Ex. oracle forms is an example of an ole Container.
What is an object group?
An object group is a container for a
group of objects; you define an object group when you want to package
related objects, so that you copy or reference them in other modules.
What is an LOV?
An LOV is a scrollable popup window that provides the operator with either a single or multi column selection list.
At what point of report execution is the before Report trigger fired?
After the query is executed but before the report is executed and the records are displayed.
What are the built -ins used for Modifying a groups structure?
ADD-GROUP_COLUMN (function)
ADD_GROUP_ROW (procedure)
DELETE_GROUP_ROW(procedure)
What is an user exit used for?
A way in which to pass control (and
possibly arguments ) form Oracle report to another Oracle products of 3
GL and then return control ( and ) back to Oracle reports.
What is the User-Named Editor?
A user named editor has the same text
editing functionality as the default editor, but, because it is a named
object, you can specify editor attributes such as windows display size,
position, and title.
My database was terminated while in BACKUP MODE, do I need to recover? (for DBA)
If a database was terminated while one of
its tablespaces was in BACKUP MODE (ALTER TABLESPACE xyz BEGIN
BACKUP;), it will tell you that media recovery is required when you try
to restart the database. The DBA is then required to recover the
database and apply all archived logs to the database. However, from
Oracle7.2, you can simply take the individual datafiles out of backup
mode and restart the database.
ALTER DATABASE DATAFILE '/path/filename' END BACKUP;
One can select from V$BACKUP to see which datafiles are in backup
mode. This normally saves a significant amount of database down time.
Thiru Vadivelu contributed the following:
From Oracle9i onwards, the following command can be used to take all of the datafiles out of hot backup mode:
ALTER DATABASE END BACKUP;
The above commands need to be issued when the database is mounted.
What is a Static Record Group?
A static record group is not associated
with a query, rather, you define its structure and row values at design
time, and they remain fixed at runtime.
What is a record group?
A record group is an internal Oracle
Forms that structure that has a column/row framework similar to a
database table. However, unlike database tables, record groups are
separate objects that belong to the form module which they are defined.
My database is down and I cannot restore. What now? (for DBA )
Recovery without any backup is normally
not supported, however, Oracle Consulting can sometimes extract data
from an offline database using a utility called DUL (Disk UnLoad). This
utility reads data in the data files and unloads it into SQL*Loader or
export dump files. DUL does not care about rollback segments, corrupted
blocks, etc, and can thus not guarantee that the data is not logically
corrupt. It is intended as an absolute last resort and will most likely
cost your company a lot of money!!!
I've lost my REDOLOG files, how can I get my DB back? (for DBA)
The following INIT.ORA parameter may be
required if your current redo logs are corrupted or blown away. Caution
is advised when enabling this parameter as you might end-up losing your
entire database. Please contact Oracle Support before using it.
_allow_resetlogs_corruption = true
What is a property clause?
A property clause is a named object that
contains a list of properties and their settings. Once you create a
property clause you can base other object on it. An object based on a
property can inherit the setting of any property in the clause that
makes sense for that object.
What is a physical page ? & What is a logical page ?
A physical page is a size of a page. That
is output by the printer. The logical page is the size of one page of
the actual report as seen in the Previewer.
I've lost some Rollback Segments, how can I get my DB back? (for DBA)
Re-start your database with the following
INIT.ORA parameter if one of your rollback segments is corrupted. You
can then drop the corrupted rollback segments and create it from
scratch.
Caution is advised when enabling this parameter, as uncommitted
transactions will be marked as committed. One can very well end up with
lost or inconsistent data!!! Please contact Oracle Support before using
it. _Corrupted_rollback_segments = (rbs01, rbs01, rbs03, rbs04)
What are the differences between EBU and RMAN? (for DBA)
Enterprise Backup Utility (EBU) is a
functionally rich, high performance interface for backing up Oracle7
databases. It is sometimes referred to as OEBU for Oracle Enterprise
Backup Utility. The Oracle Recovery Manager (RMAN) utility that ships
with Oracle8 and above is similar to Oracle7's EBU utility. However,
there is no direct upgrade path from EBU to RMAN.
How does one create a RMAN recovery catalog? (for DBA)
Start by creating a database schema
(usually called rman). Assign an appropriate tablespace to it and grant
it the recovery_catalog_owner role. Look at this example:
sqlplus sys
SQL>create user rman identified by rman;
SQL> alter user rman default tablespace tools temporary tablespace temp;
SQL> alter user rman quota unlimited on tools;
SQL> grant connect, resource, recovery_catalog_owner to rman;
SQL> exit;
Next, log in to rman and create the catalog schema. Prior to Oracle
8i this was done by running the catrman.sql script. rman catalog
rman/rman
RMAN>create catalog tablespace tools;
RMAN> exit;
You can now continue by registering your databases in the catalog. Look at this example:
rman catalog rman/rman target backdba/backdba
RMAN> register database;
How can a group in a cross products be visually distinguished from a group that does not form a cross product?
A group that forms part of a cross product will have a thicker border.
What is the frame & repeating frame?
A frame is a holder for a group of
fields. A repeating frame is used to display a set of records when the
no. of records that are to displayed is not known before.
What is a combo box?
A combo box style list item combines the
features found in list and text item. Unlike the pop list or the text
list style list items, the combo box style list item will both display
fixed values and accept one operator entered value.
What are three panes that appear in the run time pl/sql interpreter?
1. Source pane.
2. interpreter pane.
3. Navigator pane.
What are the two panes that Appear in the design time pl/sql interpreter?
1. Source pane.
2. Interpreter pane
What are the two ways by which data can be generated for a parameters list of values?
1. Using static values.
2. Writing select statement.
What are the various methods of performing a calculation in a report ?
1. Perform the calculation in the SQL statements itself.
2. Use a calculated / summary column in the data model.
What are the default extensions of the files created by menu module?
.mmb,
.mmx
What are the default extensions of the files created by forms modules?
.fmb - form module binary
.fmx - form module executable
To display the page no. for
each page on a report what would be the source & logical page no. or
& of physical page no.?
& physical page no.
It is possible to use raw devices as data files and what is the advantages over file. system files ?
Yes. The advantages over file system
files. I/O will be improved because Oracle is bye-passing the kernnel
which writing into disk. Disk Corruption will be very less.
What are disadvantages of having raw devices ?
We should depend on export/import utility
for backup/recovery (fully reliable) The tar command cannot be used for
physical file backup, instead we can use dd command which is less
flexible and has limited recoveries.
What is the significance of having storage clause ?
We can plan the storage for a table as
how much initial extents are required, how much can be extended next,
how much % should leave free for managing row updations etc.,
What is the use of INCTYPE option in EXP command ?
Type export should be performed
COMPLETE,CUMULATIVE,INCREMENTAL. List the sequence of events when a
large transaction that exceeds beyond its optimal value when an entry
wraps and causes the rollback segment toexpand into anotion Completes.
e. will be written.
What is the use of FILE option in IMP command ?
The name of the file from which import should be performed.
What is a Shared SQL pool?
The data dictionary cache is stored in an
area in SGA called the Shared SQL Pool. This will allow sharing of
parsed SQL statements among concurrent users.
What is hot backup and how it can be taken?
Taking backup of archive log files when
database is open. For this the ARCHIVELOG mode should be enabled. The
following files need to be backed up. All data files. All Archive log,
redo log files. All control files.
List the Optional Flexible
Architecture (OFA) of Oracle database? or How can we organize the
tablespaces in Oracle database to have maximum performance ?
SYSTEM - Data dictionary tables.
DATA - Standard operational tables.
DATA2- Static tables used for standard operations
INDEXES - Indexes for Standard operational tables.
INDEXES1 - Indexes of static tables used for standard operations.
TOOLS - Tools table.
TOOLS1 - Indexes for tools table.
RBS - Standard Operations Rollback Segments,
RBS1,RBS2 - Additional/Special Rollback segments.
TEMP - Temporary purpose tablespace
TEMP_USER - Temporary tablespace for users.
USERS - User tablespace.
How to implement the multiple control files for an existing database ?
Shutdown the database Copy one of the
existing control file to new location Edit Config ora file by adding new
control file. name Restart the database.
What is advantage of having disk shadowing/ Mirroring ?
Shadow set of disks save as a backup in
the event of disk failure. In most Operating System if any disk failure
occurs it automatically switchover to place of failed disk. Improved
performance because most OS support volume shadowing can direct file I/O
request to use the shadow set of files instead of the main set of
files. This reduces I/O load on the main set of disks.
How will you force database to use particular rollback segment ?
SET TRANSACTION USE ROLLBACK SEGMENT rbs_name.
Why query fails sometimes ?
Rollback segment dynamically extent to
handle larger transactions entry loads. A single transaction may wipeout
all available free space in the Rollback Segment Tablespace. This
prevents other user using Rollback segments.
What is the use of RECORD LENGTH option in EXP command ?
Record length in bytes.
How will you monitor rollback segment status ?
Querying the DBA_ROLLBACK_SEGS view
IN USE - Rollback Segment is on-line.
AVAILABLE - Rollback Segment available but not on-line.
OFF-LINE - Rollback Segment off-line
INVALID - Rollback Segment Dropped.
NEEDS RECOVERY - Contains data but need recovery or corupted.
PARTLY AVAILABLE - Contains data from an unresolved transaction involving a distributed database.
What is meant by Redo Log file mirroring ? How it can be achieved?
Process of having a copy of redo log
files is called mirroring. This can be achieved by creating group of log
files together, so that LGWR will automatically writes them to all the
members of the current on-line redo log group. If any one group fails
then database automatically switch over to next group. It degrades
performance.
Which parameter in Storage clause will reduce no. of rows per block?
PCTFREE parameter
Row size also reduces no of rows per block.
What is meant by recursive hints ?
Number of times processes repeatedly
query the dictionary table is called recursive hints. It is due to the
data dictionary cache is too small. By increasing the SHARED_POOL_SIZE
parameter we can optimize the size of Data Dictionary Cache.
What is the use of PARFILE option in EXP command ?
Name of the parameter file to be passed for export.
What is the difference between locks, latches, enqueues and semaphores? (for DBA)
A latch is an internal Oracle mechanism
used to protect data structures in the SGA from simultaneous access.
Atomic hardware instructions like TEST-AND-SET is used to implement
latches. Latches are more restrictive than locks in that they are always
exclusive. Latches are never queued, but will spin or sleep until they
obtain a resource, or time out.
Enqueues and locks are different names for the same thing. Both
support queuing and concurrency. They are queued and serviced in a
first-in-first-out (FIFO) order.
Semaphores are an operating system facility used to control
waiting. Semaphores are controlled by the following Unix parameters:
semmni, semmns and semmsl. Typical settings are:
semmns = sum of the "processes" parameter for each instance
(see init<instance>.ora for each instance)
semmni = number of instances running simultaneously;
semmsl = semmns
What is a logical backup?
Logical backup involves reading a set of
database records and writing them into a file. Export utility is used
for taking backup and Import utility is used to recover from backup.
Where can one get a list of all hidden Oracle parameters? (for DBA)
Oracle initialization or INIT.ORA
parameters with an underscore in front are hidden or unsupported
parameters. One can get a list of all hidden parameters by executing
this query:
select *
from SYS.X$KSPPI
where substr(KSPPINM,1,1) = '_';
The following query displays parameter names with their current value:
select a.ksppinm "Parameter", b.ksppstvl "Session Value", c.ksppstvl "Instance Value"
from x$ksppi a, x$ksppcv b, x$ksppsv c
where a.indx = b.indx and a.indx = c.indx
and substr(ksppinm,1,1)='_'
order by a.ksppinm;
Remember: Thou shall not play with undocumented parameters!
What is a database EVENT and how does one set it? (for DBA)
Oracle trace events are useful for
debugging the Oracle database server. The following two examples are
simply to demonstrate syntax. Refer to later notes on this page for an
explanation of what these particular events do.
Either adding them to the INIT.ORA parameter file can activate events. E.g.
event='1401 trace name errorstack, level 12'
... or, by issuing an ALTER SESSION SET EVENTS command: E.g.
alter session set events '10046 trace name context forever, level 4';
The alter session method only affects the user's current session,
whereas changes to the INIT.ORA file will affect all sessions once the
database has been restarted.
What is a Rollback segment entry ?
It is the set of before image data blocks
that contain rows that are modified by a transaction. Each Rollback
Segment entry must be completed within one rollback segment. A single
rollback segment can have multiple rollback segment entries.
What database events can be set? (for DBA)
The following events are frequently used by DBAs and Oracle Support to diagnose problems:
" 10046 trace name context forever, level 4 Trace SQL statements and show bind variables in trace output.
" 10046 trace name context forever, level 8 This shows wait events in the SQL trace files
" 10046 trace name context forever, level 12 This shows both bind variable names and wait events in the SQL trace files
" 1401 trace name errorstack, level 12 1401 trace name errorstack,
level 4 1401 trace name processstate Dumps out trace information if an
ORA-1401 "inserted value too large for column" error occurs. The 1401
can be replaced by any other Oracle Server error code that you want to
trace.
" 60 trace name errorstack level 10 Show where in the code Oracle
gets a deadlock (ORA-60), and may help to diagnose the problem.
The following lists of events are examples only. They might be version specific, so please call Oracle before using them:
" 10210 trace name context forever, level 10 10211 trace name
context forever, level 10 10231 trace name context forever, level 10
These events prevent database block corruptions
" 10049 trace name context forever, level 2 Memory protect cursor
" 10210 trace name context forever, level 2 Data block check
" 10211 trace name context forever, level 2 Index block check
" 10235 trace name context forever, level 1 Memory heap check
" 10262 trace name context forever, level 300 Allow 300 bytes memory leak for connections
Note: You can use the Unix oerr command to get the description of
an event. On Unix, you can type "oerr ora 10053" from the command prompt
to get event details.
How can one dump internal database structures? (for DBA)
The following (mostly undocumented) commands can be used to obtain information about internal database structures.
o Dump control file contents
alter session set events 'immediate trace name CONTROLF level 10'
/
o Dump file headers
alter session set events 'immediate trace name FILE_HDRS level 10'
/
o Dump redo log headers
alter session set events 'immediate trace name REDOHDR level 10'
/
o Dump the system state
NOTE: Take 3 successive SYSTEMSTATE dumps, with 10-minute intervals
alter session set events 'immediate trace name SYSTEMSTATE level 10'
/
o Dump the process state
alter session set events 'immediate trace name PROCESSSTATE level 10'
/
o Dump Library Cache details
alter session set events 'immediate trace name library cache level 10'
/
o Dump optimizer statistics whenever a SQL statement is parsed
(hint: change statement or flush pool) alter session set events '10053
trace name context forever, level 1'
/
o Dump a database block (File/ Block must be converted to DBA
address) Convert file and block number to a DBA (database block
address).
Eg: variable x varchar2;
exec :x := dbms_utility.make_data_block_address(1,12);
print x
alter session set events 'immediate trace name blockdump level 50360894'
/
What are the different kind of export backups?
Full back - Complete database
Incremental - Only affected tables from last incremental date/full backup date.
Cumulative backup - Only affected table from the last cumulative date/full backup date.
How free extents are managed in Ver 6.0 and Ver 7.0 ?
Free extents cannot be merged together in Ver 6.0.
Free extents are periodically coalesces with the neighboring free extent in Ver 7.0
What is the use of RECORD option in EXP command?
For Incremental exports, the flag indirects whether a record will be stores data dictionary tables recording the export.
What is the use of ROWS option in EXP command ?
Flag to indicate whether table rows should be exported. If 'N' only DDL statements for the database objects will be created.
What is the use of COMPRESS option in EXP command ?
Flag to indicate whether export should compress fragmented segments into single extents.
How will you swap objects into a different table space for an existing database ?
Export the user
Perform import using the command imp system/manager file=export.dmp indexfile=newrite.sql.
This will create all definitions into newfile.sql. Drop necessary objects.
Run the script newfile.sql after altering the tablespaces.
Import from the backup for the necessary objects.
How does Space allocation table place within a block ?
Each block contains entries as follows
Fixed block header
Variable block header
Row Header,row date (multiple rows may exists)
PCTEREE (% of free space for row updation in future)
What are the factors causing the reparsing of SQL statements in SGA?
Due to insufficient Shared SQL pool size.
Monitor the ratio of the reloads takes place while executing SQL
statements. If the ratio is greater than 1 then increase the
SHARED_POOL_SIZE. LOGICAL & PHYSICAL ARCHITECTURE OF DATABASE.
What is dictionary cache ?
Dictionary cache is information about the databse objects stored in a data dictionary table.
What is a Control file ?
Database overall physical architecture is
maintained in a file called control file. It will be used to maintain
internal consistency and guide recovery operations. Multiple copies of
control files are advisable.
What is Database Buffers ?
Database buffers are cache in the SGA
used to hold the data blocks that are read from the data segments in the
database such as tables, indexes and clusters DB_BLOCK_BUFFERS
parameter in INIT.ORA decides the size.
How will you create multiple rollback segments in a database ?
Create a database which implicitly
creates a SYSTEM Rollback Segment in a SYSTEM tablespace. Create a
Second Rollback Segment name R0 in the SYSTEM tablespace. Make new
rollback segment available (After shutdown, modify init.ora file and
Start database) Create other tablespaces (RBS) for rollback segments.
Deactivate Rollback Segment R0 and activate the newly created rollback
segments.
What is cold backup? What are the elements of it?
Cold backup is taking backup of all physical files after normal shutdown of database. We need to take.
- All Data files.
- All Control files.
- All on-line redo log files.
- The init.ora file (Optional)
What is meant by redo log buffer ?
Changes made to entries are written to
the on-line redo log files. So that they can be used in roll forward
operations during database recoveries. Before writing them into the redo
log files, they will first brought to redo log buffers in SGA and LGWR
will write into files frequently. LOG_BUFFER parameter will decide the
size.
How will you estimate the space required by a non-clustered tables?
Calculate the total header size
Calculate the available dataspace per data block
Calculate the combined column lengths of the average row
Calculate the total average row size.
Calculate the average number rows that can fit in a block
Calculate the number of blocks and bytes required for the table.
After arriving the calculation, add 10 % additional space to calculate the initial extent size for a working table.
How will you monitor the space allocation ?
By querying DBA_SEGMENT table/view.
What is meant by free extent ?
A free extent is a collection of
continuous free blocks in tablespace. When a segment is dropped its
extents are reallocated and are marked as free.
What is the use of IGNORE option in IMP command ?
A flag to indicate whether the import should ignore errors encounter when issuing CREATE commands.
What is the use of ANALYSE ( Ver 7) option in EXP command ?
A flag to indicate whether statistical information about the exported objects should be written to export dump file.
What is the use of ROWS option in IMP command ?
A flag to indicate whether rows should be imported. If this is set to 'N' then only DDL for database objects will be executed.
What is the use of INDEXES option in EXP command ?
A flag to indicate whether indexes on tables will be exported.
What is the use of INDEXES option in IMP command ?
A flag to indicate whether import should import index on tables or not.
What is the use of GRANT option in EXP command?
A flag to indicate whether grants on databse objects will be exported or not. Value is 'Y' or 'N'.
What is the use of GRANT option in IMP command ?
A flag to indicate whether grants on database objects will be imported.
What is the use of FULL option in EXP command ?
A flag to indicate whether full databse export should be performed.
What is the use of SHOW option in IMP command ?
A flag to indicate whether file content should be displayed or not.
What is the use of CONSTRAINTS option in EXP command ?
A flag to indicate whether constraints on table need to be exported.
What is the use of CONSISTENT (Ver 7) option in EXP command ?
A flag to indicate whether a read consistent version of all the exported objects should be maintained.
What are the different methods of backing up oracle database ?
- Logical Backups
- Cold Backups
- Hot Backups (Archive log)
What is the difference between ON-VALIDATE-FIELD trigger and a POST-CHANGE trigger ?
When you changes the Existing value to
null, the On-validate field trigger will fire post change trigger will
not fire. At the time of execute-query post-change trigger will fire,
on-validate field trigger will not fire.
When is PRE-QUERY trigger executed ?
When Execute-query or count-query Package procedures are invoked.
How do you trap the error in forms 3.0 ?
using On-Message or On-Error triggers.
How many pages you can in a single form ?
Unlimited
While specifying master/detail relationship between two blocks specifying the join condition is a must ?
True or False. ?
True
EXIT_FORM is a restricted package procedure ?
a. True b. False
True
What is the usage of an ON-INSERT,ON-DELETE and ON-UPDATE TRIGGERS ?
These triggers are executes when
inserting, deleting and updating operations are performed and can be
used to change the default function of insert, delete or update
respectively. For Eg, instead of inserting a row in a table an existing
row can be updated in the same table.
What are the types of Pop-up window ?
the pop-up field editor
pop-up list of values
pop-up pages.
Alert :
What is an SQL *FORMS ?
SQL *forms is 4GL tool for developing and executing; Oracle based interactive application.
How do you control the constraints in forms ?
Select the use constraint property is ON Block definition screen.
BLOCK
What is the difference between restricted and unrestricted package procedure ?
Restricted package procedure that affects
the basic functions of SQL * Forms. It cannot used in all triggers
except key triggers. Unrestricted package procedure that does not
interfere with the basic functions of SQL * Forms it can be used in any
triggers.
A query fetched 10 records How many times does a PRE-QUERY Trigger and POST-QUERY Trigger will get executed ?
PRE-QUERY fires once.
POST-QUERY fires 10 times.
Give the sequence in which
triggers fired during insert operations, when the following 3 triggers
are defined at the same block level ?
a. ON-INSERT b. POST-INSERT c. PRE-INSERT
State the order in which these triggers are executed ?
POST-FIELD,ON-VALIDATE-FIELD,POST-CHANGE and KEY-NEXTFLD. KEY-NEXTFLD,POST-CHANGE, ON-VALIDATE-FIELD, POST-FIELD. g.
What the PAUSE package procedure does ?
Pause suspends processing until the operator presses a function key
What do you mean by a page ?
Pages are collection of display information, such as constant text and graphics
What are the type of User Exits ?
ORACLE Precompliers user exits
OCI (ORACLE Call Interface)
Non-ORACEL user exits.
Page :
What is the difference between an ON-VALIDATE-FIELD trigger and a trigger ?
On-validate-field trigger fires, when the
field Validation status New or changed. Post-field-trigger whenever the
control leaving form the field, it will fire.
Can we use a restricted package procedure in ON-VALIDATE-FIELD Trigger ?
No
Is a Key startup trigger fires as result of a operator pressing a key explicitly ?
No
Can we use GO-BLOCK package in a pre-field trigger ?
No
Can we create two blocks with the same name in form 3.0 ?
No
What does an on-clear-block Trigger fire?
It fires just before SQL * forms the current block.
Name the two files that are created when you generate the form give the filex extension ?
INP (Source File)
FRM (Executable File)
What package procedure used for invoke sql *plus from sql *forms ?
Host (E.g. Host (sqlplus))
What is the significance of PAGE 0 in forms 3.0 ?
Hide the fields for internal calculation.
What are the different types of key triggers ?
Function Key
Key-function
Key-others
Key-startup
What is the difference between a Function Key Trigger and Key Function Trigger ?
Function key triggers are associated with
individual SQL*FORMS function keys You can attach Key function triggers
to 10 keys or key sequences that normally do not perform any SQL *
FORMS operations. These keys referred as key F0 through key F9.
Committed block sometimes refer to a BASE TABLE ?
False
Error_Code is a package proecdure ?
a. True b. false
False
When is cost based optimization triggered? (for DBA)
It's important to have statistics on
all tables for the CBO (Cost Based Optimizer) to work correctly. If one
table involved in a statement does not have statistics, Oracle has to
revert to rule-based optimization for that statement. So you really want
for all tables to have statistics right away; it won't help much to
just have the larger tables analyzed.
Generally, the CBO can change the execution plan when you:
1. Change statistics of objects by doing an ANALYZE;
2. Change some initialization parameters (for example: hash_join_enabled, sort_area_size, db_file_multiblock_read_count).
How can one optimize %XYZ% queries? (for DBA)
It is possible to improve %XYZ% queries
by forcing the optimizer to scan all the entries from the index instead
of the table. This can be done by specifying hints. If the index is
physically smaller than the table (which is usually the case) it will
take less time to scan the entire index than to scan the entire table.
What Enter package procedure does ?
Enter Validate-data in the current validation unit.
Where can one find I/O statistics per table? (for DBA)
The UTLESTAT report shows I/O per
tablespace but one cannot see what tables in the tablespace has the most
I/O. The $ORACLE_HOME/rdbms/admin/catio.sql script creates a sample_io
procedure and table to gather the required information. After executing
the procedure, one can do a simple SELECT * FROM io_per_object; to
extract the required information. For more details, look at the header
comments in the $ORACLE_HOME/rdbms/admin/catio.sql script.
My query was fine last week and now it is slow. Why? (for DBA)
The likely cause of this is because the
execution plan has changed. Generate a current explain plan of the
offending query and compare it to a previous one that was taken when the
query was performing well. Usually the previous plan is not available.
Some factors that can cause a plan to change are:
. Which tables are currently analyzed? Were they previously analyzed? (ie. Was the query using RBO and now CBO?)
. Has OPTIMIZER_MODE been changed in INIT.ORA?
. Has the DEGREE of parallelism been defined/changed on any table?
. Have the tables been re-analyzed? Were the tables analyzed using estimate or compute? If estimate, what percentage was used?
. Have the statistics changed?
. Has the INIT.ORA parameter DB_FILE_MULTIBLOCK_READ_COUNT been changed?
. Has the INIT.ORA parameter SORT_AREA_SIZE been changed?
. Have any other INIT.ORA parameters been changed?
. What do you think the plan should be? Run the query with hints to see if this produces the required performance.
Why is Oracle not using the damn index? (for DBA)
This problem normally only arises when
the query plan is being generated by the Cost Based Optimizer. The usual
cause is because the CBO calculates that executing a Full Table Scan
would be faster than accessing the table via the index.
Fundamental things that can be checked are:
. USER_TAB_COLUMNS.NUM_DISTINCT - This column defines the number of distinct values the column holds.
. USER_TABLES.NUM_ROWS - If NUM_DISTINCT = NUM_ROWS then using an
index would be preferable to doing a FULL TABLE SCAN. As the
NUM_DISTINCT decreases, the cost of using an index increase thereby is
making the index less desirable.
. USER_INDEXES.CLUSTERING_FACTOR - This defines how ordered the
rows are in the index. If CLUSTERING_FACTOR approaches the number of
blocks in the table, the rows are ordered. If it approaches the number
of rows in the table, the rows are randomly ordered. In such a case, it
is unlikely that index entries in the same leaf block will point to rows
in the same data blocks.
. Decrease the INIT.ORA parameter DB_FILE_MULTIBLOCK_READ_COUNT - A
higher value will make the cost of a FULL TABLE SCAN cheaper.
. Remember that you MUST supply the leading column of an index, for
the index to be used (unless you use a FAST FULL SCAN or SKIP
SCANNING).
. There are many other factors that affect the cost, but sometimes
the above can help to show why an index is not being used by the CBO. If
from checking the above you still feel that the query should be using
an index, try specifying an index hint. Obtain an explain plan of the
query either using TKPROF with TIMED_STATISTICS, so that one can see the
CPU utilization, or with AUTOTRACE to see the statistics. Compare this
to the explain plan when not using an index.
When should one rebuild an index? (for DBA)
You can run the 'ANALYZE INDEX VALIDATE
STRUCTURE' command on the affected indexes - each invocation of this
command creates a single row in the INDEX_STATS view. This row is
overwritten by the next ANALYZE INDEX command, so copy the contents of
the view into a local table after each ANALYZE. The 'badness' of the
index can then be judged by the ratio of 'DEL_LF_ROWS' to 'LF_ROWS'.
What are the unrestricted procedures used to change the popup screen position during run time ?
Anchor-view
Resize -View
Move-View.
What is an Alert ?
An alert is window that appears in the middle of the screen overlaying a portion of the current display.
Deleting a page removes information about all the fields in that page ?
a. True. b. False
a. True.
Two popup pages can appear on the screen at a time ?Two popup pages can appear on the screen at a time ?
a. True. b. False?
a. True.
Classify the restricted and unrestricted procedure from the following.
a. Call
b. User-Exit
c. Call-Query
d. Up
e. Execute-Query
f. Message
g. Exit-From
h. Post
i. Break?
a. Call - unrestricted
b. User Exit - Unrestricted
c. Call_query - Unrestricted
d. Up - Restricted
e. Execute Query - Restricted
f. Message - Restricted
g. Exit_form - Restricted
h. Post - Restricted
i. Break - Unrestricted.
What is an User Exits ?
A user exit is a subroutine which are
written in programming languages using pro*C pro *Cobol , etc., that
link into the SQL * forms executable.
What is a Trigger ?
A piece of logic that is executed at or triggered by a SQL *forms event.
What is a Package Procedure ?
A Package procedure is built in PL/SQL procedure.
What is the maximum size of a form ?
255 character width and 255 characters Length.
What is the difference between system.current_field and system.cursor_field ?
1. System.current_field gives name of the field.
2. System.cursor_field gives name of the field with block name.
List the system variables related in Block and Field?
1. System.block_status
2. System.current_block
3. System.current_field
4. System.current_value
5. System.cursor_block
6. System.cursor_field
7. System.field_status.
What are the different types of Package Procedure ?
1. Restricted package procedure.
2. Unrestricted package procedure.
What are the types of TRIGGERS ?
1. Navigational Triggers.
2. Transaction Triggers.
Identify package function from the following ?
1. Error-Code
2. Break
3. Call
4. Error-text
5. Form-failure
6. Form-fatal
7. Execute-query
8. Anchor View
9. Message_code?
1. Error_Code
2. Error_Text
3. Form_Failure
4. Form_Fatal
5. Message_Code
Can you attach an lov to a field at run-time? if yes, give the build-in name.?
Yes. Set_item_proprety
Is it possible to attach same library to more than one form?
Yes
Can you attach an lov to a field at design time?
Yes
List the windows event triggers available in Forms 4.0?
When-window-activated,
when-window-closed,
when-window-deactivated,
when-window-resized
What are the triggers associated with the image item?
When-Image-activated(Fires when the operator double clicks on an image Items)
When-image-pressed(fires when the operator selects or deselects the image item)
What is a visual attribute?
Visual Attributes are the font, color and
pattern characteristics of objects that operators see and intract with
in our application.
How many maximum number of radio buttons can you assign to a radio group?
Unlimited no of radio buttons can be assigned to a radio group
How do you pass the parameters from one form to another form?
To pass one or more parameters to a
called form, the calling form must perform the following steps in a
trigger or user named routine execute the create_parameter_list built-in
function to programmatically. Create a parameter list to execute the
add parameter built-in procedure to add one or more parameters list.
Execute the call_form, New_form or run_product built_in procedure and
include the name or id of the parameter list to be passed to the called
form.
What is a Layout Editor?
The Layout Editor is a graphical design
facility for creating and arranging items and boilerplate text and
graphics objects in your application's interface.
List the Types of Items?
Text item.
Chart item.
Check box.
Display item.
Image item.
List item.
Radio Group.
User Area item.
List system variables available in forms 4.0, and not available in forms 3.0?
System.cordination_operation
System Date_threshold
System.effective_Date
System.event_window
System.suppress_working
What are the display styles of an alert?
Stop, Caution, note
What built-in is used for showing the alert during run-time?
Show_alert.
What built-in is used for changing the properties of the window dynamically?
Set_window_property
Canvas-View
What are the different types of windows?
Root window, secondary window.
What is a predefined exception available in forms 4.0?
Raise form_trigger_failure
What is a radio Group?
Radio groups display a fixed no of options that are mutually Exclusive. User can select one out of n number of options.
What are the different type of a record group?
Query record group
Static record group
Non query record group
What are the menu items that oracle forms 4.0 supports?
Plain, Check,Radio, Separator, Magic
Give the equivalent term in forms 4.0 for the following. Page, Page 0?
Page - Canvas-View
Page 0 - Canvas-view null.
What triggers are associated with the radio group?
Only when-radio-changed trigger associated with radio group
Visual Attributes.
What are the triggers associated with a check box?
Only When-checkbox-activated Trigger associated with a Check box.
Can you attach an alert to a field?
No
Can a root window be made modal?
No
What is a list item?
It is a list of text elements.
List some built-in routines used to manipulate images in image_item?
Image_add
Image_and
Image_subtract
Image_xor
Image_zoom
Can you change the alert messages at run-time?
If yes, give the name of the built-in to change the alert messages at run-time. Yes. Set_alert_property.
What is the built-in used to get and set lov properties during run-time?
Get_lov_property
Set_lov_property
Record Group
What is the built-in routine used to count the no of rows in a group?
Get_group _row_count
System Variables
Give the Types of modules in a form?
Form
Menu
Library
Write the Abbreviation for the following File Extension 1. FMB 2. MMB 3. PLL?
FMB ----- Form Module Binary.
MMB ----- Menu Module Binary.
PLL ------ PL/SQL Library Module Binary.
List the built-in routine for controlling window during run-time?
Find_window,
get_window_property,
hide_window,
move_window,
resize_window,
set_window_property,
show_View
List the built-in routine for controlling window during run-time?
Find_canvas
Get-Canvas_property
Get_view_property
Hide_View
Replace_content_view
Scroll_view
Set_canvas_property
Set_view_property
Show_view
Alert
What is the built-in function used for finding the alert?
Find_alert
Editors
List the editors availables in forms 4.0?
Default editor
User_defined editors
system editors.
What buil-in routines are used to display editor dynamically?
Edit_text item
show_editor
LOV
What is an Lov?
A list of values is a single or multi column selection list displayed in a pop-up window
What is a record Group?
A record group is an internal oracle forms data structure that has a similar column/row frame work to a database table
Give built-in routine related to a record groups?
Create_group (Function)
Create_group_from_query(Function)
Delete_group(Procedure)
Add_group_column(Function)
Add_group_row(Procedure)
Delete_group_row(Procedure)
Populate_group(Function)
Populate_group_with_query(Function)
Set_group_Char_cell(procedure)
List the built-in routines for the controlling canvas views during run-time?
Find_canvas
Get-Canvas_property
Get_view_property
Hide_View
Replace_content_view
Scroll_view
Set_canvas_property
Set_view_property
Show_view
Alert
System.effective_date system variable is read only True/False?
False
What are the built_in used to trapping errors in forms 4?
Error_type return character
Error_code return number
Error_text return char
Dbms_error_code return no.
Dbms_error_text return char
What is Oracle Financials? (for DBA)
Oracle Financials products provide
organizations with solutions to a wide range of long- and short-term
accounting system issues. Regardless of the size of the business, Oracle
Financials can meet accounting management demands with:
Oracle Assets: Ensures that an organization's property and
equipment investment is accurate and that the correct asset tax
accounting strategies are chosen.
Oracle General Ledger: Offers a complete solution to journal entry,
budgeting, allocations, consolidation, and financial reporting needs.
Oracle Inventory: Helps an organization make better inventory decisions by minimizing stock and maximizing cash flow.
Oracle Order Entry: Provides organizations with a sophisticated order entry system for managing customer commitments.
Oracle Payables: Lets an organization process more invoices with
fewer staff members and tighter controls. Helps save money through
maximum discounts, bank float, and prevention of duplicate payment.
Oracle Personnel: Improves the management of employee- related
issues by retaining and making available every form of personnel data.
Oracle Purchasing: Improves buying power, helps negotiate bigger
discounts, eliminates paper flow, increases financial controls, and
increases productivity.
Oracle Receivables:. Improves cash flow by letting an organization
process more payments faster, without off-line research. Helps correctly
account for cash, reduce outstanding receivables, and improve
collection effectiveness.
Oracle Revenue Accounting Gives an organization timely and accurate revenue and flexible commissions reporting.
Oracle Sales Analysis: Allows for better forecasting, planning. and reporting of sales information.
What are the design facilities available in forms 4.0?
Default Block facility.
Layout Editor.
Menu Editor.
Object Lists.
Property Sheets.
PL/SQL Editor.
Tables Columns Browser.
Built-ins Browser.
What is the most important module in Oracle Financials? (for DBA)
The General Ledger (GL) module is the
basis for all other Oracle Financial modules. All other modules provide
information to it. If you implement Oracle Financials, you should switch
your current GL system first.GL is relatively easy to implement. You
should go live with it first to give your implementation team a chance
to be familiar with Oracle Financials.
What are the types of canvas-views?
Content View, Stacked View.
What is the MultiOrg and what is it used for? (for DBA)
MultiOrg or Multiple Organizations
Architecture allows multiple operating units and their relationships to
be defined within a single installation of Oracle Applications. This
keeps each operating unit's transaction data separate and secure.
Use the following query to determine if MuliOrg is intalled:
select multi_org_flag from fnd_product_groups;
What is the difference between Fields and FlexFields? (for DBA)
A field is a position on a form that one
uses to enter, view, update, or delete information. A field prompt
describes each field by telling what kind of information appears in the
field, or alternatively, what kind of information should be entered in
the field.
A flexfield is an Oracle Applications field made up of segments.
Each segment has an assigned name and a set of valid values. Oracle
Applications uses flexfields to capture information about your
organization. There are two types of flexfields: key flexfields and
descriptive flexfields.
Explain types of Block in forms4.0?
Base table Blocks.
Control Blocks.
1. A base table block is one that is associated with a specific database table or view.
2. A control block is a block that is not associated with a database table. ITEMS
What is an Alert?
An alert is a modal window that displays a message notifies the operator of some application condition
What are the built-in routines is available in forms 4.0 to create and manipulate a parameter list?
Add_parameter
Create_Parameter_list
Delete_parameter
Destroy_parameter_list
Get_parameter_attr
Get_parameter_list
set_parameter_attr
What is a record Group?
A record group is an internal oracle forms data structure that has a similar column/row frame work to a database table
What is a Navigable item?
A navigable item is one that operators
can navigate to with the keyboard during default navigation, or that
Oracle forms can navigate to by executing a navigational built-in
procedure.
What is a library in Forms 4.0?
A library is a collection of Pl/SQL program units, including user named procedures, functions & packages
How image_items can be populate to field in forms 4.0?
A fetch from a long raw database column
PL/Sql assignment to executing the read_image_file built_in procedure to
get an image from the file system.
What is the content view and stacked view?
A content view is the "Base" view that
occupies the entire content pane of the window in which it is displayed.
A stacked view differs from a content canvas view in that it is not the
base view for the window to which it is assigned
What is a Check Box?
A Check Box is a two state control
that indicates whether a certain condition or value is on or off, true
or false. The display state of a check box is always either "checked" or
"unchecked".
What is a canvas-view?
A canvas-view is the background object on
which you layout the interface items (text-items, check boxes, radio
groups, and so on.) and boilerplate objects that operators see and
interact with as they run your form. At run-time, operators can see only
those items that have been assigned to a specific canvas. Each canvas,
in term, must be displayed in a specific window.
Explain the following file extension related to library?
.pll,.lib,.pld
The library pll files is a portable design file comparable to an fmb form file
The library lib file is a plat form specific, generated library file comparable to a fmx form file
The pld file is Txt format file and can be used for source controlling your library files Parameter
Explain the usage of WHERE CURRENT OF clause in cursors ?
WHERE CURRENT OF clause in an UPDATE,DELETE statement refers to the latest row fetched from a cursor. Database Triggers
Name the tables where characteristics of Package, procedure and functions are stored ?
User_objects, User_Source and User_error.
Explain the two type of Cursors ?
There are two types of cursors, Implicit
Cursor and Explicit Cursor. PL/SQL uses Implicit Cursors for queries.
User defined cursors are called Explicit Cursors. They can be declared
and used.
What are two parts of package ?
The two parts of package are PACKAGE
SPECIFICATION & PACKAGE BODY. Package Specification contains
declarations that are global to the packages and local to the schema.
Package Body contains actual procedures and local declaration of the
procedures and cursor declarations.
What are two virtual tables available during database trigger execution ?
The table columns are referred as OLD.column_name and NEW.column_name.
For triggers related to INSERT only NEW.column_name values only available.
For triggers related to UPDATE only OLD.column_name NEW.column_name values only available.
For triggers related to DELETE only OLD.column_name values only available.
What is Fine Grained Auditing? (for DBA)
Fine Grained Auditing (DBMS_FGA) allows
auditing records to be generated when certain rows are selected from a
table. A list of defined policies can be obtained from
DBA_AUDIT_POLICIES. Audit records are stored in DBA_FGA_AUDIT_TRAIL.
Look at this example:
o Add policy on table with autiting condition...
execute dbms_fga.add_policy('HR', 'EMP', 'policy1', 'deptno > 10');
o Must ANALYZE, this feature works with CBO (Cost Based Optimizer)
analyze table EMP compute statistics;
select * from EMP where c1 = 11; -- Will trigger auditing
select * from EMP where c1 = 09; -- No auditing
o Now we can see the statments that triggered the auditing condition...
select sqltext from sys.fga_log$;
delete from sys.fga_log$;
What is a package ? What are the advantages of packages ? What is Pragma EXECPTION_INIT ? Explain the usage ?
The PRAGMA EXECPTION_INIT tells the
complier to associate an exception with an oracle error. To get an error
message of a specific oracle error. e.g. PRAGMA EXCEPTION_INIT
(exception name, oracle error number)
What is a Virtual Private Database? (for DBA)
Oracle 8i introduced the notion of a
Virtual Private Database (VPD). A VPD offers Fine-Grained Access Control
(FGAC) for secure separation of data. This ensures that users only have
access to data that pertains to them. Using this option, one could even
store multiple companies' data within the same schema, without them
knowing about it. VPD configuration is done via the DBMS_RLS (Row Level
Security) package. Select from SYS.V$VPD_POLICY to see existing VPD
configuration.
What is Raise_application_error ?
Raise_application_error is a procedure of
package DBMS_STANDARD which allows to issue an user_defined error
messages from stored sub-program or database trigger.
What is Oracle Label Security? (for DBA)
Oracle Label Security (formerly called
Trusted Oracle MLS RDBMS) uses the VPD (Virtual Private Database)
feature of Oracle8i to implement row level security. Access to rows are
restricted according to a user's security sensitivity tag or label.
Oracle Label Security is configured, controlled and managed from the
Policy Manager, an Enterprise Manager-based GUI utility.
Give the structure of the procedure ?
PROCEDURE name (parameter list.....)
is
local variable declarations
BEGIN
Executable statements.
Exception.
exception handlers
end;
What is OEM (Oracle Enterprise Manager)? (for DBA)
OEM is a set of systems management tools
provided by Oracle Corporation for managing the Oracle environment. It
provides tools to monitor the Oracle environment and automate tasks
(both one-time and repetitive in nature) to take database administration
a step closer to "Lights Out" management.
Question What is PL/SQL ?
PL/SQL is a procedural language that has
both interactive SQL and procedural programming language constructs such
as iteration, conditional branching.
What are the components of OEM? (for DBA)
Oracle Enterprise Manager (OEM) has the following components:
. Management Server (OMS): Middle tier server that handles
communication with the intelligent agents. The OEM Console connects to
the management server to monitor and configure the Oracle enterprise.
. Console: This is a graphical interface from where one can
schedule jobs, events, and monitor the database. The console can be
opened from a Windows workstation, Unix XTerm (oemapp command) or Web
browser session (oem_webstage).
. Intelligent Agent (OIA): The OIA runs on the target database and
takes care of the execution of jobs and events scheduled through the
Console.
What happens if a procedure that updates a column of table X is called in a database trigger of the same table ?
Mutation of table occurs.
Is it possible to use Transaction control Statements such a ROLLBACK or COMMIT in Database Trigger ? Why ?
It is not possible. As triggers are
defined for each table, if you use COMMIT of ROLLBACK in a trigger, it
affects logical transaction processing.
How many types of database triggers can be specified on a table ? What are they ?
Insert Update Delete
Before Row o.k. o.k. o.k.
After Row o.k. o.k. o.k.
Before Statement o.k. o.k. o.k.
After Statement o.k. o.k. o.k.
If FOR EACH ROW clause is specified, then the trigger for each Row affected by the statement.
If WHEN clause is specified, the trigger fires according to the returned Boolean value.
What are the modes of parameters that can be passed to a procedure ?
IN,OUT,IN-OUT parameters.
Where the Pre_defined_exceptions are stored ?
In the standard package.
Procedures, Functions & Packages ;
Write the order of precedence for validation of a column in a table ?
I. done using Database triggers.
ii. done using Integarity Constraints.?
I & ii.
Give the structure of the function ?
FUNCTION name (argument list .....) Return datatype is
local variable declarations
Begin
executable statements
Exception
execution handlers
End;
Explain how procedures and functions are called in a PL/SQL block ?
Function is called as part of an expression.
sal := calculate_sal ('a822');
procedure is called as a PL/SQL statement
calculate_bonus ('A822');
What are advantages fo Stored Procedures?
Extensibility,Modularity, Reusability, Maintainability and one time compilation.
What is an Exception ? What are types of Exception ?
Exception is the error handling part of
PL/SQL block. The types are Predefined and user defined. Some of
Predefined exceptions are.
CURSOR_ALREADY_OPEN
DUP_VAL_ON_INDEX
NO_DATA_FOUND
TOO_MANY_ROWS
INVALID_CURSOR
INVALID_NUMBER
LOGON_DENIED
NOT_LOGGED_ON
PROGRAM-ERROR
STORAGE_ERROR
TIMEOUT_ON_RESOURCE
VALUE_ERROR
ZERO_DIVIDE
OTHERS.
What are the PL/SQL Statements used in cursor processing ?
DECLARE CURSOR name, OPEN cursor name, FETCH cursor name INTO or Record types, CLOSE cursor name.
What are the components of a PL/SQL Block ?
Declarative part, Executable part and Exception part.
Datatypes PL/SQL
What is a database trigger ? Name some usages of database trigger ?
Database trigger is stored PL/SQL program
unit associated with a specific database table. Usages are Audit data
modifications, Log events transparently, Enforce complex business rules
Derive column values automatically, Implement complex security
authorizations. Maintain replicate tables.
What is a cursor ? Why Cursor is required ?
Cursor is a named private SQL area from
where information can be accessed. Cursors are required to process rows
individually for queries returning multiple rows.
What is a cursor for loop ?
Cursor for loop implicitly declares
%ROWTYPE as loop index, opens a cursor, fetches rows of values from
active set into fields in the record and closes when all the records
have been processed.
e.g.. FOR emp_rec IN C1 LOOP
salary_total := salary_total +emp_rec sal;
END LOOP;
What will happen after commit statement ?
Cursor C1 is
Select empno,
ename from emp;
Begin
open C1; loop
Fetch C1 into
eno.ename;
Exit When
C1 %notfound;-----
commit;
end loop;
end;
The cursor having query as SELECT .... FOR UPDATE gets closed after COMMIT/ROLLBACK.
The cursor having query as SELECT.... does not get closed even after COMMIT/ROLLBACK.
How packaged procedures and functions are called from the following?
a. Stored procedure or anonymous block
b. an application program such a PRC *C, PRO* COBOL
c. SQL *PLUS??
a. PACKAGE NAME.PROCEDURE NAME (parameters);
variable := PACKAGE NAME.FUNCTION NAME (arguments);
EXEC SQL EXECUTE
b.BEGIN
PACKAGE NAME.PROCEDURE NAME (parameters)
variable := PACKAGE NAME.FUNCTION NAME (arguments);
END;
END EXEC;
c. EXECUTE PACKAGE NAME.PROCEDURE if the procedures does not have any out/in-out parameters. A function can not be called.
What is a stored procedure ?
A stored procedure is a sequence of statements that perform specific function.
What are the components of a PL/SQL block ?
A set of related declarations and procedural statements is called block.
What is difference between a PROCEDURE & FUNCTION ?
A FUNCTION is always returns a value using the return statement.
A PROCEDURE may return one or more values through parameters or may not return at all.
What is difference between a Cursor declared in a procedure and Cursor declared in a package specification ?
A cursor declared in a package specification is global and can be accessed by other procedures or procedures in a package.
A cursor declared in a procedure is local to the procedure that can not be accessed by other procedures.
What are the cursor attributes used in PL/SQL ?
%ISOPEN - to check whether cursor is open or not
% ROWCOUNT - number of rows fetched/updated/deleted.
% FOUND - to check whether cursor has fetched any row. True if rows are fetched.
% NOT FOUND - to check whether cursor has fetched any row. True if no rows are featched.
These attributes are proceeded with SQL for Implicit Cursors and with Cursor name for Explicit Cursors.
What are % TYPE and % ROWTYPE ? What are the advantages of using these over datatypes?
% TYPE provides the data type of a variable or a database column to that variable.
% ROWTYPE provides the record type that represents a entire row of a table or view or columns selected in the cursor.
The advantages are :
I. Need not know about variable's data type
ii. If the database definition of a column in a table changes, the data type of a variable changes accordingly.
What is difference between % ROWTYPE and TYPE RECORD ?
% ROWTYPE is to be used whenever query returns a entire row of a table or view.
TYPE rec RECORD is to be used whenever query returns columns of different table or views and variables.
E.g. TYPE r_emp is RECORD (eno emp.empno% type,ename emp ename %type );
e_rec emp% ROWTYPE
cursor c1 is select empno,deptno from emp;
e_rec c1 %ROWTYPE.
What are the different types of PL/SQL program units that can be defined and stored in ORACLE database ?
Procedures and Functions,Packages and Database Triggers.
What are the advantages of having a Package ?
Increased functionality (for
example,global package variables can be declared and used by any
proecdure in the package) and performance (for example all objects of
the package are parsed compiled, and loaded into memory once)
What are the uses of Database Trigger ?
Database triggers can be used to
automatic data generation, audit data modifications, enforce complex
Integrity constraints, and customize complex security authorizations.
What is a Procedure ?
A Procedure consist of a set of SQL and
PL/SQL statements that are grouped together as a unit to solve a
specific problem or perform a set of related tasks.
What is a Package ?
A Package is a collection of related
procedures, functions, variables and other package constructs together
as a unit in the database.
What is difference between Procedures and Functions ?
A Function returns a value to the caller where as a Procedure does not.
What is Database Trigger ?
A Database Trigger is procedure (set of
SQL and PL/SQL statements) that is automatically executed as a result of
an insert in, update to, or delete from a table.
Can the default values be assigned to actual parameters?
Yes
Can a primary key contain more than one columns?
Yes
What is an UTL_FILE.What are different procedures and functions associated with it?
UTL_FILE is a package that adds the
ability to read and write to operating system files. Procedures
associated with it are FCLOSE, FCLOSE_ALL and 5 procedures to output
data to a file PUT, PUT_LINE, NEW_LINE, PUTF, FFLUSH.PUT,
FFLUSH.PUT_LINE,FFLUSH.NEW_LINE. Functions associated with it are FOPEN,
ISOPEN.
What are ORACLE PRECOMPILERS?
Using ORACLE PRECOMPILERS, SQL statements
and PL/SQL blocks can be contained inside 3GL programs written in
C,C++,COBOL,PASCAL, FORTRAN,PL/1 AND ADA. The Precompilers are known as
Pro*C,Pro*Cobol,... This form of PL/SQL is known as embedded pl/sql,the
language in which pl/sql is embedded is known as the host language. The
prcompiler translates the embedded SQL and pl/sql statements into calls
to the precompiler runtime library. The output must be compiled and
linked with this library to creator an executable.
Differentiate between TRUNCATE and DELETE?
TRUNCATE deletes much faster than DELETE
TRUNCATE
DELETE
It is a DDL statement
It is a DML statement
It is a one way trip, cannot ROLLBACK
One can Rollback
Doesn't have selective features (where clause)
Has
Doesn't fire database triggers
Does
It requires disabling of referential constraints.
What is difference between a formal and an actual parameter?
The variables declared in the procedure
and which are passed, as arguments are called actual, the parameters in
the procedure declaration. Actual parameters contain the values that are
passed to a procedure and receive results. Formal parameters are the
placeholders for the values of actual parameters
What should be the return type for a cursor variable. Can we use a scalar data type as return type?
The return type for a cursor must be a
record type.It can be declared explicitly as a user-defined or %ROWTYPE
can be used. eg TYPE t_studentsref IS REF CURSOR RETURN
students%ROWTYPE
What are different Oracle database objects?
-TABLES
-VIEWS
-INDEXES
-SYNONYMS
-SEQUENCES
-TABLESPACES etc
What is difference between SUBSTR and INSTR?
SUBSTR returns a specified portion of a
string eg SUBSTR('BCDEF',4) output BCDE INSTR provides character
position in which a pattern is found in a string. eg
INSTR('ABC-DC-F','-',2) output 7 (2nd occurence of '-')
Display the number value in Words?
SQL> select sal, (to_char(to_date(sal,'j'), 'jsp'))
from emp;
the output like,
SAL (TO_CHAR(TO_DATE(SAL,'J'),'JSP'))
--------- ----------------------------------------
800 eight hundred
1600 one thousand six hundred
1250 one thousand two hundred fifty
If you want to add some text like, Rs. Three Thousand only.
SQL> select sal "Salary ",
(' Rs. '|| (to_char(to_date(sal,'j'), 'Jsp'))|| ' only.'))
"Sal in Words" from emp
/
Salary Sal in Words
------- -----------------------------------------------
800 Rs. Eight Hundred only.
1600 Rs. One Thousand Six Hundred only.
1250 Rs. One Thousand Two Hundred Fifty only.
What is difference between SQL and SQL*PLUS?
SQL*PLUS is a command line tool where as
SQL and PL/SQL language interface and reporting tool. Its a command line
tool that allows user to type SQL commands to be executed directly
against an Oracle database. SQL is a language used to query the
relational database(DML,DCL,DDL). SQL*PLUS commands are used to format
query result, Set options, Edit SQL commands and PL/SQL.
What are various joins used while writing SUBQUERIES?
Self join-Its a join foreign key of a
table references the same table. Outer Join--Its a join condition used
where One can query all the rows of one of the tables in the join
condition even though they don't satisfy the join condition.
Equi-join--Its a join condition that retrieves rows from one or
more tables in which one or more columns in one table are equal to one
or more columns in the second table.
What a SELECT FOR UPDATE cursor represent.?
SELECT......FROM......FOR......UPDATE[OF column-reference][NOWAIT]
The processing done in a fetch loop modifies the rows that have
been retrieved by the cursor. A convenient way of modifying the rows is
done by a method with two parts: the FOR UPDATE clause in the cursor
declaration, WHERE CURRENT OF CLAUSE in an UPDATE or declaration
statement.
What are various privileges that a user can grant to another user?
-SELECT
-CONNECT
-RESOURCES
Display the records between two range?
select rownum, empno, ename from emp
where rowid in (select rowid from emp where rownum <=&upto minus
select rowid from emp where rownum<&Start);
minvalue.sql Select the Nth lowest value from a table?
select level, min('col_name') from my_table where level = '&n' connect by prior ('col_name') < 'col_name')
group by level;
Example:
Given a table called emp with the following columns:
-- id number
-- name varchar2(20)
-- sal number
--
-- For the second lowest salary:
-- select level, min(sal) from emp
-- where level=2
-- connect by prior sal < sal
-- group by level
What is difference between Rename and Alias?
Rename is a permanent name given to a
table or column whereas Alias is a temporary name given to a table or
column which do not exist once the SQL statement is executed.
Difference between an implicit & an explicit cursor.?
only one row. However,queries that return
more than one row you must declare an explicit cursor or use a cursor
FOR loop. Explicit cursor is a cursor in which the cursor name is
explicitly assigned to a SELECT statement via the CURSOR...IS statement.
An implicit cursor is used for all SQL statements Declare, Open, Fetch,
Close. An explicit cursors are used to process multirow SELECT
statements An implicit cursor is used to process INSERT, UPDATE, DELETE
and single row SELECT. .INTO statements.
What is a OUTER JOIN?
Outer Join--Its a join condition used
where you can query all the rows of one of the tables in the join
condition even though they don’t satisfy the join condition.
What is a cursor?
Oracle uses work area to execute SQL
statements and store processing information PL/SQL construct called a
cursor lets you name a work area and access its stored information A
cursor is a mechanism used to fetch more than one row in a Pl/SQl block.
What is the purpose of a cluster?
Oracle does not allow a user to
specifically locate tables, since that is a part of the function of the
RDBMS. However, for the purpose of increasing performance, oracle allows
a developer to create a CLUSTER. A CLUSTER provides a means for storing
data from different tables together for faster retrieval than if the
table placement were left to the RDBMS.
What is OCI. What are its uses?
Oracle Call Interface is a method of
accesing database from a 3GL program. Uses--No precompiler is
required,PL/SQL blocks are executed like other DML statements.
The OCI library provides
--functions to parse SQL statemets
--bind input variables
--bind output variables
--execute statements
--fetch the results
How you open and close a cursor variable. Why it is required?
OPEN cursor variable FOR SELECT...Statement
CLOSE cursor variable In order to associate a cursor variable with a
particular SELECT statement OPEN syntax is used. In order to free the
resources used for the query CLOSE statement is used.
Display Odd/ Even number of records?
Odd number of records:
select * from emp where (rowid,1) in (select rowid, mod(rownum,2) from emp);
Output:-
1
3
5
Even number of records:
select * from emp where (rowid,0) in (select rowid, mod(rownum,2) from emp)
Output:-
2
4
6
What are various constraints used in SQL?
-NULL
-NOT NULL
-CHECK
-DEFAULT
Can cursor variables be stored in PL/SQL tables. If yes how. If not why?
No, a cursor variable points a row which cannot be stored in a two-dimensional PL/SQL table.
Difference between NO DATA FOUND and %NOTFOUND?
NO DATA FOUND is an exception raised only
for the SELECT....INTO statements when the where clause of the
querydoes not match any rows. When the where clause of the explicit
cursor does not match any rows the %NOTFOUND attribute is set to TRUE
instead.
Can you use a commit statement within a database trigger?
No
What WHERE CURRENT OF clause does in a cursor?
LOOP
SELECT num_credits INTO v_numcredits FROM classes
WHERE dept=123 and course=101;
UPDATE students
FHKO;;;;;;;;;SET current_credits=current_credits+v_numcredits
WHERE CURRENT OF X;
There is a string 120000 12 0 .125 , how you will find the position of the decimal place?
INSTR('120000 12 0 .125',1,'.')
output 13
What are different modes of parameters used in functions and procedures?
-IN -OUT -INOUT
How you were passing cursor variables in PL/SQL 2.2?
In PL/SQL 2.2 cursor variables cannot be
declared in a package.This is because the storage for a cursor variable
has to be allocated using Pro*C or OCI with version 2.2, the only means
of passing a cursor variable to a PL/SQL block is via bind variable or a
procedure parameter.
When do you use WHERE clause and when do you use HAVING clause?
HAVING clause is used when you want to
specify a condition for a group function and it is written after GROUP
BY clause. The WHERE clause is used when you want to specify a condition
for columns, single row functions except group functions and it is
written before GROUP BY clause if it is used.
Difference between procedure and function.?
Functions are named PL/SQL blocks that
return a value and can be called with arguments procedure a named block
that can be called with parameter. A procedure all is a PL/SQL statement
by itself, while a Function call is called as part of an expression.
Which is more faster - IN or EXISTS?
EXISTS is more faster than IN because EXISTS returns a Boolean value whereas IN returns a value.
What is syntax for dropping a procedure and a function .Are these operations possible?
Drop Procedure procedure_name
Drop Function function_name
How will you delete duplicating rows from a base table?
delete from table_name where rowid not in
(select max(rowid) from table group by duplicate_values_field_name); or
delete duplicate_values_field_name dv from table_name ta where rowid
<(select min(rowid) from table_name tb where ta.dv=tb.dv);
Difference between database triggers and form triggers?
-Data base trigger(DBT) fires when a DML
operation is performed on a data base table. Form trigger(FT) Fires when
user presses a key or navigates between fields on the screen
-Can be row level or statement level No distinction between row level and statement level.
-Can manipulate data stored in Oracle tables via SQL Can manipulate data in Oracle tables as well as variables in forms.
-Can be fired from any session executing the triggering DML statements. Can be fired only from the form that define the trigger.
-Can cause other database triggers to fire. Can cause other database triggers to fire, but not other form triggers.
What is a cursor for loop?
Cursor For Loop is a loop where oracle
implicitly declares a loop variable, the loop index that of the same
record type as the cursor's record.
How you will avoid duplicating records in a query?
By using DISTINCT
What is a view ?
A view is stored procedure based on one or more tables, it’s a virtual table.
What is difference between UNIQUE and PRIMARY KEY constraints?
A table can have only one PRIMARY KEY
whereas there can be any number of UNIQUE keys. The columns that compose
PK are automatically define NOT NULL, whereas a column that compose a
UNIQUE is not automatically defined to be mandatory must also specify
the column is NOT NULL.
What is use of a cursor variable? How it is defined?
A cursor variable is associated with
different statements at run time, which can hold different values at run
time. Static cursors can only be associated with one run time query. A
cursor variable is reference type (like a pointer in C).
Declaring a cursor variable:
TYPE type_name IS REF CURSOR RETURN return_type type_name is the
name of the reference type,return_type is a record type indicating the
types of the select list that will eventually be returned by the cursor
variable.
How do you find the numbert of rows in a Table ?
A bad answer is count them (SELECT COUNT(*) FROM table_name)
A good answer is :-
'By generating SQL to ANALYZE TABLE table_name COUNT STATISTICS by
querying Oracle System Catalogues (e.g. USER_TABLES or ALL_TABLES).
The best answer is to refer to the utility which Oracle released
which makes it unnecessary to do ANALYZE TABLE for each Table
individually.
What is the maximum buffer size that can be specified using the DBMS_OUTPUT.ENABLE function?
1,000,00
What are cursor attributes?
-%ROWCOUNT
-%NOTFOUND
-%FOUND
-%ISOPEN
There is a % sign in one field of a column. What will be the query to find it?
'' Should be used before '%'.
What is ON DELETE CASCADE ?
When ON DELETE CASCADE is specified
ORACLE maintains referential integrity by automatically removing
dependent foreign key values if a referenced primary or unique key value
is removed.
What is the fastest way of accessing a row in a table ?
Using ROWID.CONSTRAINTS
What is difference between TRUNCATE & DELETE ?
TRUNCATE commits after deleting entire
table i.e., can not be rolled back. Database triggers do not fire on
TRUNCATEDELETE allows the filtered deletion. Deleted records can be
rolled back or committed. Database triggers fire on DELETE.
What is a transaction ?
Transaction is logical unit between two commits and commit and rollback.
What are the advantages of VIEW ?
To protect some of the columns of a table from other users.To hide complexity of a query.To hide complexity of calculations.
How will you a activate/deactivate integrity constraints ?
The integrity constraints can be enabled or disabled by ALTER TABLE ENABLE constraint/DISABLE constraint.
Where the integrity constraints are stored in Data Dictionary ?
The integrity constraints are stored in USER_CONSTRAINTS.
What is the Subquery ?
Sub query is a query whose return values are used in filtering conditions of the main query.
How to access the current
value and next value from a sequence ? Is it possible to access the
current value in a session before accessing next value ?
Sequence name CURRVAL, Sequence name
NEXTVAL.It is not possible. Only if you access next value in the
session, current value can be accessed.
What are the usage of SAVEPOINTS ?value in a session before accessing next value ?
SAVEPOINTS are used to subdivide a
transaction into smaller parts. It enables rolling back part of a
transaction. Maximum of five save points are allowed.
What is ROWID ?in a session before accessing next value ?
ROWID is a pseudo column attached to each
row of a table. It is 18 character long, blockno, rownumber are the
components of ROWID.
Explain Connect by Prior ?in a session before accessing next value ?
Retrieves rows in hierarchical order.e.g. select empno, ename from emp where.
How many LONG columns are allowed in a table ? Is it possible to use LONG columns in WHERE clause or ORDER BY ?
Only one LONG columns is allowed. It is not possible to use LONG column in WHERE or ORDER BY clause.
What is Referential Integrity ?
Maintaining data integrity through a set
of rules that restrict the values of one or more columns of the tables
based on the values of primary key or unique key of the referenced
table.
What is a join ? Explain the different types of joins ?
Join is a query which retrieves related
columns or rows from multiple tables.Self Join - Joining the table with
itself.Equi Join - Joining two tables by equating two common
columns.Non-Equi Join - Joining two tables by equating two common
columns.Outer Join - Joining two tables in such a way that query can
also retrieve rows that do not have corresponding join value in the
other table.
If an unique key constraint on DATE column is created, will it validate the rows that are inserted with SYSDATE ?
It won't, Because SYSDATE format contains time attached with it.
How does one stop and start the OMS? (for DBA)
Use the following command sequence to stop and start the OMS (Oracle Management Server):
oemctl start oms
oemctl status oms sysman/oem_temp
oemctl stop oms sysman/oem_temp
Windows NT/2000 users can just stop and start the required
services. The default OEM administrator is "sysman" with a password of
"oem_temp".
NOTE: Use command oemctrl instead of oemctl for Oracle 8i and below.
What is an Integrity Constraint ?
Integrity constraint is a rule that restricts values to a column in a table.
How does one create a repository? (for DBA)
For OEM v2 and above, start the Oracle
Enterprise Manager Configuration Assistant (emca on Unix) to create and
configure the management server and repository. Remember to setup a
backup for the repository database after creating it.
If a View on a single base table is manipulated will the changes be reflected on the base table ?
If changes are made to the tables which are base tables of a view will the changes be reference on the view.
The following describes means to create a OEM V1.x (very old!!!) repository on WindowsNT:
. Create a tablespace that would hold the repository data. A size
between 200- 250 MB would be ideal. Let us call it Dummy_Space.
. Create an Oracle user who would own this repository. Assign DBA,
SNMPAgent, Exp_Full_database, Imp_Full_database roles to this user. Lets
call this user Dummy_user. Assign Dummy_Space as the default
tablespace.
. Create an operating system user with the same name as the Oracle
username. I.e. Dummy_User. Add 'Log on as a batch job' under advanced
rights in User manager.
. Fire up Enterprise manager and log in as Dummy_User and enter the
password. This would trigger the creation of the repository. From now
on, Enterprise manager is ready to accept jobs.
What is a database link ?
Database Link is a named path through which a remote database can be accessed.
How does one list one's databases in the OEM Console? (for DBA)
Follow these steps to discover databases and other services from the OEM Console:
1. Ensure the GLOBAL_DBNAME parameter is set for all databases in
your LISTENER.ORA file (optional). These names will be listed in the OEM
Console. Please note that names entered are case sensitive. A portion
of a listener.ora file:
(SID_DESC =
(GLOBAL_DBNAME = DB_name_for_OEM)
(SID_NAME = ...
2. Start the Oracle Intelligent Agent on the machine you want to
discover. See section "How does one start the Oracle Intelligent
Agent?".
3. Start the OEM Console, navigate to menu "Navigator/ Discover
Nodes". The OEM Discovery Wizard will guide you through the process of
discovering your databases and other services.
What is CYCLE/NO CYCLE in a Sequence ?
CYCLE specifies that the sequence
continues to generate values after reaching either maximum or minimum
value. After pan ascending sequence reaches its maximum value, it
generates its minimum value. After a descending sequence reaches its
minimum, it generates its maximum.NO CYCLE specifies that the sequence
cannot generate more values after reaching its maximum or minimum value.
What is correlated sub-query ?
Correlated sub query is a sub query which has reference to the main query.
What are the data types allowed in a table ?
CHAR,VARCHAR2,NUMBER,DATE,RAW,LONG and LONG RAW.
What is difference between CHAR and VARCHAR2 ? What is the maximum SIZE allowed for each type ?
CHAR pads blank spaces to the maximum length. VARCHAR2 does not pad blank spaces. For CHAR it is 255 and 2000 for VARCHAR2.
Can a view be updated/inserted/deleted? If Yes under what conditions ?
A View can be updated/deleted/inserted if
it has only one base table if the view is based on columns from one or
more tables then insert, update and delete is not possible.
What are the different types of Coordinations of the Master with the Detail block?
POPULATE_GROUP(function)
POPULATE_GROUP_WITH_QUERY(function)
SET_GROUP_CHAR_CELL(procedure)
SET_GROUPCELL(procedure)
SET_GROUP_NUMBER_CELL(procedure)
Use the ADD_GROUP_COLUMN function to add a column to a record group that was created at design time?
I) TRUE II) FALSE
II) FALSE
Use the ADD_GROUP_ROW procedure to add a row to a static record group?
I) TRUE II) FALSE
I) FALSE
maxvalue.sql Select the Nth Highest value from a table?
select level, max('col_name') from my_table where level = '&n' connect by prior ('col_name') > 'col_name')
group by level;
Example:
Given a table called emp with the following columns:
-- id number
-- name varchar2(20)
-- sal number
--
-- For the second highest salary:
-- select level, max(sal) from emp
-- where level=2
-- connect by prior sal > sal
-- group by level
Find out nth highest salary from emp table?
SELECT DISTINCT (a.sal) FROM EMP A WHERE &N = (SELECT COUNT (DISTINCT (b.sal)) FROM EMP B WHERE a.sal<=b.sal);
For E.g.:-
Enter value for n: 2
SAL
---------
3700
Suppose a customer table is
having different columns like customer no, payments.What will be the
query to select top three max payments?
SELECT customer_no, payments from customer C1
WHERE 3<=(SELECT COUNT(*) from customer C2
WHERE C1.payment <= C2.payment)
How you will avoid your query from using indexes?
SELECT * FROM emp
Where emp_no+' '=12345;
i.e you have to concatenate the column name with space within codes in the where condition.
SELECT /*+ FULL(a) */ ename, emp_no from emp
where emp_no=1234;
i.e using HINTS
What utility is used to create a physical backup?
Either rman or alter tablespace begin backup will do..
What are the Back ground processes in Oracle and what are they.
This is one of the most frequently asked
question.There are basically 9 Processes but in a general system we need
to mention the first five background processes.They do the house
keeping activities for the Oracle and are common in any system.
The various background processes in oracle are
a) Data Base Writer(DBWR) :: Data Base Writer Writes Modified
blocks from Database buffer cache to Data Files.This is required since
the data is not written whenever a transaction is committed.
b)LogWriter(LGWR) :: LogWriter writes the redo log entries to disk.
Redo Log data is generated in redo log buffer of SGA. As transaction
commits and log buffer fills, LGWR writes log entries into a online redo
log file.
c) System Monitor(SMON) :: The System Monitor performs instance
recovery at instance startup. This is useful for recovery from system
failure
d)Process Monitor(PMON) :: The Process Monitor performs process
recovery when user Process fails. Pmon Clears and Frees resources that
process was using.
e) CheckPoint(CKPT) :: At Specified times, all modified database
buffers in SGA are written to data files by DBWR at Checkpoints and
Updating all data files and control files of database to indicate the
most recent checkpoint
f)Archieves(ARCH) :: The Archiver copies online redo log files to archival storal when they are busy.
g) Recoveror(RECO) :: The Recoveror is used to resolve the distributed transaction in network
h) Dispatcher (Dnnn) :: The Dispatcher is useful in Multi Threaded Architecture
i) Lckn :: We can have upto 10 lock processes for inter instance locking in parallel sql.
How many types of Sql Statements are there in Oracle
There are basically 6 types of sql statments.They are
a) Data Definition Language(DDL) :: The DDL statements define and maintain objects and drop objects.
b) Data Manipulation Language(DML) :: The DML statements manipulate database data.
c) Transaction Control Statements :: Manage change by DML
d) Session Control :: Used to control the properties of current
session enabling and disabling roles and changing .e.g. :: Alter
Statements, Set Role
e) System Control Statements :: Change Properties of Oracle Instance .e.g.:: Alter System
f) Embedded Sql :: Incorporate DDL, DML and T.C.S in Programming
Language.e.g:: Using the Sql Statements in languages such as 'C', Open,
Fetch, execute and close
What is a Transaction in Oracle
A transaction is a Logical unit of work
that compromises one or more SQL Statements executed by a single User.
According to ANSI, a transaction begins with first executable statement
and ends when it is explicitly committed or rolled back.
Key Words Used in Oracle
The Key words that are used in Oracle are ::
a) Committing :: A transaction is said to be committed when the
transaction makes permanent changes resulting from the SQL statements.
b) Rollback :: A transaction that retracts any of the changes resulting from SQL statements in Transaction.
c) SavePoint :: For long transactions that contain many SQL
statements, intermediate markers or savepoints are declared. Savepoints
can be used to divide a transaction into smaller points.
d) Rolling Forward :: Process of applying redo log during recovery is called rolling forward.
e) Cursor :: A cursor is a handle ( name or a pointer) for the
memory associated with a specific stamen. A cursor is basically an area
allocated by Oracle for executing the Sql Statement. Oracle uses an
implicit cursor statement for Single row query and Uses Explicit cursor
for a multi row query.
f) System Global Area(SGA) :: The SGA is a shared memory region
allocated by the Oracle that contains Data and control information for
one Oracle Instance. It consists of Database Buffer Cache and Redo log
Buffer.
g) Program Global Area (PGA) :: The PGA is a memory buffer that contains data and control information for server process.
g) Database Buffer Cache :: Database Buffer of SGA stores the most
recently used blocks of database data. The set of database buffers in an
instance is called Database Buffer Cache.
h) Redo log Buffer :: Redo log Buffer of SGA stores all the redo log entries.
i) Redo Log Files :: Redo log files are set of files that protect
altered database data in memory that has not been written to Data Files.
They are basically used for backup when a database crashes.
j) Process :: A Process is a 'thread of control' or mechanism in Operating System that executes series of steps.
What are Procedure, functions and Packages ?
Procedures and functions consist of
set of PL/SQL statements that are grouped together as a unit to solve a
specific problem or perform set of related tasks.
Procedures do not Return values while Functions return one One
Value Packages :: Packages Provide a method of encapsulating and storing
related procedures, functions, variables and other Package Contents
What are Database Triggers and Stored Procedures
Database Triggers :: Database Triggers
are Procedures that are automatically executed as a result of insert in,
update to, or delete from table.
Database triggers have the values old and new to denote the old
value in the table before it is deleted and the new indicated the new
value that will be used. DT are useful for implementing complex business
rules which cannot be enforced using the integrity rules.We can have
the trigger as Before trigger or After Trigger and at Statement or Row
level. e.g:: operations insert,update ,delete 3 before ,after 3*2 A
total of 6 combinatons
At statment level(once for the trigger) or row level( for every
execution ) 6 * 2 A total of 12. Thus a total of 12 combinations are
there and the restriction of usage of 12 triggers has been lifted from
Oracle 7.3 Onwards.
Stored Procedures :: Stored Procedures are Procedures that are
stored in Compiled form in the database.The advantage of using the
stored procedures is that many users can use the same procedure in
compiled and ready to use format.
How many Integrity Rules are there and what are they
There are Three Integrity Rules. They are as follows ::
a) Entity Integrity Rule :: The Entity Integrity Rule enforces that the Primary key cannot be Null
b) Foreign Key Integrity Rule :: The FKIR denotes that the
relationship between the foreign key and the primary key has to be
enforced.When there is data in Child Tables the Master tables cannot be
deleted.
c) Business Integrity Rules :: The Third Intigrity rule is about
the complex business processes which cannot be implemented by the above 2
rules.
What are the Various Master and Detail Relation ships.
The various Master and Detail Relationship are
a) NonIsolated :: The Master cannot be deleted when a child is exisiting
b) Isolated :: The Master can be deleted when the child is exisiting
c) Cascading :: The child gets deleted when the Master is deleted.
What are the Various Block Coordination Properties
The various Block Coordination Properties are
a) Immediate Default Setting. The Detail records are shown when the Master Record are shown.
b) Deffered with Auto Query Oracle Forms defer fetching the detail records until the operator navigates to the detail block.
c) Deffered with No Auto Query The operator must navigate to the detail block and explicitly execute a query
What are the Different Optimization Techniques
The Various Optimisation techniques are
a) Execute Plan :: we can see the plan of the query and change it accordingly based on the indexes
b) Optimizer_hint ::
set_item_property('DeptBlock',OPTIMIZER_HINT,'FIRST_ROWS');
Select /*+ First_Rows */ Deptno,Dname,Loc,Rowid from dept
where (Deptno > 25)
c) Optimize_Sql ::
By setting the Optimize_Sql = No, Oracle Forms assigns a single
cursor for all SQL statements.This slow downs the processing because for
evertime the SQL must be parsed whenver they are executed.
f45run module = my_firstform userid = scott/tiger optimize_sql = No
d) Optimize_Tp ::
By setting the Optimize_Tp= No, Oracle Forms assigns seperate
cursor only for each query SELECT statement. All other SQL statements
reuse the cursor.
f45run module = my_firstform userid = scott/tiger optimize_Tp = No
How does one change an Oracle user's password?(for DBA)
Issue the following SQL command:
ALTER USER <username> IDENTIFIED BY <new_password>;
From Oracle8 you can just type "password" from SQL*Plus, or if you
need to change another user's password, type "password user_name". Look
at this example:
SQL> password
Changing password for SCOTT
Old password:
New password:
Retype new password:
How does one create and drop database users?
Look at these examples:
CREATE USER scott
IDENTIFIED BY tiger -- Assign password
DEFAULT TABLESACE tools -- Assign space for table and index segments
TEMPORARY TABLESPACE temp; -- Assign sort space
DROP USER scott CASCADE; -- Remove user
After creating a new user, assign the required privileges:
GRANT CONNECT, RESOURCE TO scott;
GRANT DBA TO scott; -- Make user a DB Administrator
Remember to give the user some space quota on its tablespaces:
ALTER USER scott QUOTA UNLIMITED ON tools;
Who created all these users in my database?/ Can I drop this user? (for DBA)
Oracle creates a number of default database users or schemas when a new database is created. Below are a few of them:
SYS/CHANGE_ON_INSTALL or INTERNAL
Oracle Data Dictionary/ Catalog
Created by: ?/rdbms/admin/sql.bsq and various cat*.sql scripts
Can password be changed: Yes (Do so right after the database was created)
Can user be dropped: NO
SYSTEM/MANAGER
The default DBA user name (please do not use SYS)
Created by: ?/rdbms/admin/sql.bsq
Can password be changed: Yes (Do so right after the database was created)
Can user be dropped: NO
OUTLN/OUTLN
Stored outlines for optimizer plan stability
Created by: ?/rdbms/admin/sql.bsq
Can password be changed: Yes (Do so right after the database was created)
Can user be dropped: NO
SCOTT/TIGER, ADAMS/WOOD, JONES/STEEL, CLARK/CLOTH and BLAKE/PAPER.
Training/ demonstration users containing the popular EMP and DEPT tables
Created by: ?/rdbms/admin/utlsampl.sql
Can password be changed: Yes
Can user be dropped: YES - Drop users cascade from all production environments
HR/HR (Human Resources), OE/OE (Order Entry), SH/SH (Sales History).
Training/ demonstration users containing the popular EMPLOYEES and DEPARTMENTS tables
Created by: ?/demo/schema/mksample.sql
Can password be changed: Yes
Can user be dropped: YES - Drop users cascade from all production environments
CTXSYS/CTXSYS
Oracle interMedia (ConText Cartridge) administrator user
Created by: ?/ctx/admin/dr0csys.sql
TRACESVR/TRACE
Oracle Trace server
Created by: ?/rdbms/admin/otrcsvr.sql
DBSNMP/DBSNMP
Oracle Intelligent agent
Created by: ?/rdbms/admin/catsnmp.sql, called from catalog.sql
Can password be changed: Yes - put the new password in snmp_rw.ora file
Can user be dropped: YES - Only if you do not use the Intelligent Agents
ORDPLUGINS/ORDPLUGINS
Object Relational Data (ORD) User used by Time Series, etc.
Created by: ?/ord/admin/ordinst.sql
ORDSYS/ORDSYS
Object Relational Data (ORD) User used by Time Series, etc
Created by: ?/ord/admin/ordinst.sql
DSSYS/DSSYS
Oracle Dynamic Services and Syndication Server
Created by: ?/ds/sql/dssys_init.sql
MDSYS/MDSYS
Oracle Spatial administrator user
Created by: ?/ord/admin/ordinst.sql
AURORA$ORB$UNAUTHENTICATED/INVALID
Used for users who do not authenticate in Aurora/ORB
Created by: ?/javavm/install/init_orb.sql called from ?/javavm/install/initjvm.sql
PERFSTAT/PERFSTAT
Oracle Statistics Package (STATSPACK) that supersedes UTLBSTAT/UTLESTAT
Created by: ?/rdbms/admin/statscre.sql
Remember to change the passwords for the SYS and SYSTEM users immediately after installation!
Except for the user SYS, there should be no problem altering these users to use a different default and temporary tablespace.
How does one enforce strict password control? (for DBA)
By default Oracle's security is not
extremely good. For example, Oracle will allow users to choose single
character passwords and passwords that match their names and userids.
Also, passwords don't ever expire. This means that one can hack an
account for years without ever locking the user.
From Oracle8 one can manage passwords through profiles. Some of the things that one can restrict:
. FAILED_LOGIN_ATTEMPTS - failed login attempts before the account is locked
. PASSWORD_LIFE_TIME - limits the number of days the same password can be used for authentication
. PASSWORD_REUSE_TIME - number of days before a password can be reused
. PASSWORD_REUSE_MAX - number of password changes required before the current password can be reused
. PASSWORD_LOCK_TIME - number of days an account will be locked after maximum failed login attempts
. PASSWORD_GRACE_TIME - number of days after the grace period begins during which a warning is issued and login is allowed
. PASSWORD_VERIFY_FUNCTION - password complexity verification script
Look at this simple example:
CREATE PROFILE my_profile LIMIT
PASSWORD_LIFE_TIME 30;
ALTER USER scott PROFILE my_profile;
How does one switch to another user in Oracle? (for DBA)
Users normally use the "connect"
statement to connect from one database user to another. However, DBAs
can switch from one user to another without a password. Of course it is
not advisable to bridge Oracle's security, but look at this example:
SQL> select password from dba_users where username='SCOTT';
PASSWORD
F894844C34402B67
SQL> alter user scott identified by lion;
User altered.
SQL> connect scott/lion
Connected.
REM Do whatever you like...
SQL> connect system/manager
Connected.
SQL> alter user scott identified by values 'F894844C34402B67';
User altered.
SQL> connect scott/tiger
Connected.
Note: Also see the su.sql script in the Useful Scripts and Sample Programs Page.
What are snap shots and views
Snapshots are mirror or replicas of
tables. Views are built using the columns from one or more tables. The
Single Table View can be updated but the view with multi table cannot be
updated
What are the OOPS concepts in Oracle.
Oracle does implement the OOPS concepts.
The best example is the Property Classes. We can categorize the
properties by setting the visual attributes and then attach the property
classes for the objects. OOPS supports the concepts of objects and
classes and we can consider the property classes as classes and the
items as objects
What is the difference between candidate key, unique key and primary key
Candidate keys are the columns in the
table that could be the primary keys and the primary key is the key that
has been selected to identify the rows. Unique key is also useful for
identifying the distinct rows in the table.)
What is concurrency
Concurrency is allowing simultaneous access of same data by different users. Locks useful for accesing the database are
a) Exclusive
The exclusive lock is useful for locking the row when an
insert,update or delete is being done.This lock should not be applied
when we do only select from the row.
b) Share lock
We can do the table as Share_Lock as many share_locks can be put on the same resource.
Previleges and Grants
Previleges are the right to execute a
particulare type of SQL statements. e.g :: Right to Connect, Right to
create, Right to resource Grants are given to the objects so that the
object might be accessed accordingly.The grant has to be given by the
owner of the object
Table Space,Data Files,Parameter File, Control Files
Table Space :: The table space is useful
for storing the data in the database.When a database is created two
table spaces are created.
a) System Table space :: This data file stores all the tables related to the system and dba tables
b) User Table space :: This data file stores all the user related tables
We should have seperate table spaces for storing the tables and indexes so that the access is fast.
Data Files :: Every Oracle Data Base has one or more physical data
files.They store the data for the database.Every datafile is associated
with only one database.Once the Data file is created the size cannot
change.To increase the size of the database to store more data we have
to add data file.
Parameter Files :: Parameter file is needed to start an instance.A
parameter file contains the list of instance configuration parameters
e.g.::
db_block_buffers = 500
db_name = ORA7
db_domain = u.s.acme lang
Control Files :: Control files record the physical structure of the data files and redo log files
They contain the Db name, name and location of dbs, data files ,redo log files and time stamp.
Physical Storage of the Data
The finest level of granularity of the data base are the data blocks.
Data Block :: One Data Block correspond to specific number of physical database space
Extent :: Extent is the number of specific number of contigious data blocks.
Segments :: Set of Extents allocated for Extents. There are three types of Segments
a) Data Segment :: Non Clustered Table has data segment data of every table is stored in cluster data segment
b) Index Segment :: Each Index has index segment that stores data
c) Roll Back Segment :: Temporarily store 'undo' information
What are the Pct Free and Pct Used
Pct Free is used to denote the percentage
of the free space that is to be left when creating a table. Similarly
Pct Used is used to denote the percentage of the used space that is to
be used when creating a table
eg.:: Pctfree 20, Pctused 40
What is Row Chaining
The data of a row in a table may not be able to fit the same data block.Data for row is stored in a chain of data blocks .
What is a 2 Phase Commit
Two Phase commit is used in distributed
data base systems. This is useful to maintain the integrity of the
database so that all the users see the same values. It contains DML
statements or Remote Procedural calls that reference a remote object.
There are basically 2 phases in a 2 phase commit.
a) Prepare Phase :: Global coordinator asks participants to prepare
b) Commit Phase :: Commit all participants to coordinator to Prepared, Read only or abort Reply
What is the difference between deleting and truncating of tables
Deleting a table will not remove the rows
from the table but entry is there in the database dictionary and it can
be retrieved But truncating a table deletes it completely and it cannot
be retrieved.
What are mutating tables
When a table is in state of transition it
is said to be mutating. eg :: If a row has been deleted then the table
is said to be mutating and no operations can be done on the table except
select.
What are Codd Rules
Codd Rules describe the ideal nature of a
RDBMS. No RDBMS satisfies all the 12 codd rules and Oracle Satisfies 11
of the 12 rules and is the only Rdbms to satisfy the maximum number of
rules.
What is Normalisation
Normalisation is the process of organising the tables to remove the redundancy.There are mainly 5 Normalisation rules.
a) 1 Normal Form :: A table is said to be in 1st Normal Form when the attributes are atomic
b) 2 Normal Form :: A table is said to be in 2nd Normal Form when all the candidate keys are dependant on the primary key
c) 3rd Normal Form :: A table is said to be third Normal form when it is not dependant transitively
What is the Difference between a post query and a pre query
A post query will fire for every row that is fetched but the pre query will fire only once.
Deleting the Duplicate rows in the table
We can delete the duplicate rows in the table by using the Rowid
Can U disable database trigger? How?
Yes. With respect to table
ALTER TABLE TABLE
[[ DISABLE all_trigger ]]
What is pseudo columns ? Name them?
A pseudocolumn behaves like a table
column, but is not actually stored in the table. You can select from
pseudocolumns, but you cannot insert, update, or delete their values.
This section describes these pseudocolumns:
* CURRVAL
* NEXTVAL
* LEVEL
* ROWID
* ROWNUM
How many columns can table have?
The number of columns in a table can range from 1 to 254.
Is space acquired in blocks or extents ?
In extents .
What is clustered index?
In an indexed cluster, rows are stored together based on their cluster key values . Can not applied for HASH.
What are the datatypes supported By oracle (INTERNAL)?
Varchar2, Number,Char , MLSLABEL.
What are attributes of cursor?
%FOUND , %NOTFOUND , %ISOPEN,%ROWCOUNT
Can you use select in FROM clause of SQL select ?
Yes.
Which trigger are created when master -detail relay?
master delete property
* NON-ISOLATED (default)
a) on check delete master
b) on clear details
c) on populate details
* ISOLATED
a) on clear details
b) on populate details
* CASCADE
a) per-delete
b) on clear details
c) on populate details
which system variables can be set by users?
SYSTEM.MESSAGE_LEVEL
SYSTEM.DATE_THRESHOLD
SYSTEM.EFFECTIVE_DATE
SYSTEM.SUPPRESS_WORKING
What are object group?
An object group is a container for a
group of objects. You define an object group when you want to package
related objects so you can copy or reference them in another module.
What are referenced objects?
Referencing allows you to create objects
that inherit their functionality and appearance from other objects.
Referencing an object is similar to copying an object, except that the
resulting reference object maintains a link to its source object. A
reference object automatically inherits any changes that have been made
to the source object when you open or regenerate the module that
contains the reference object.
Can you store objects in library?
Referencing allows you to create objects
that inherit their functionality and appearance from other objects.
Referencing an object is similar to copying an object, except that the
resulting reference object maintains a link to its source object. A
reference object automatically inherits any changes that have been made
to the source object when you open or regenerate the module that
contains the reference object.
Is forms 4.5 object oriented tool ? why?
yes , partially. 1) PROPERTY CLASS - inheritance property 2) OVERLOADING : procedures and functions.
Can you issue DDL in forms?
yes, but you have to use FORMS_DDL.
Referencing allows you to create objects that inherit their
functionality and appearance from other objects. Referencing an object
is similar to copying an object, except that the resulting reference
object maintains a link to its source object. A reference object
automatically inherits any changes that have been made to the source
object when you open or regenerate the module that contains the
reference object. Any string expression up to 32K:
- a literal
- an expression or a variable representing the text of a block of dynamically created PL/SQL code
- a DML statement or
- a DDL statement
Restrictions:
The statement you pass to FORMS_DDL may not contain bind variable
references in the string, but the values of bind variables can be
concatenated into the string before passing the result to FORMS_DDL.
What is SECURE property?
- Hides characters that the operator types into the text item. This setting is typically used for password protection.
What are the types of triggers and how the sequence of firing in text item
Triggers can be classified as Key Triggers, Mouse Triggers ,Navigational Triggers.
Key Triggers :: Key Triggers are fired as a result of Key action.e.g :: Key-next-field, Key-up,Key-Down
Mouse Triggers :: Mouse Triggers are fired as a result of the mouse
navigation.e.g. When-mouse-button-presed,when-mouse-doubleclicked,etc
Navigational Triggers :: These Triggers are fired as a result of Navigation. E.g. : Post-Text-item,Pre-text-item.
We also have event triggers like when ?new-form-instance and when-new-block-instance.
We cannot call restricted procedures like go_to(?my_block.first_item?) in the Navigational triggers
But can use them in the Key-next-item.
The Difference between Key-next and Post-Text is an very important
question. The key-next is fired as a result of the key action while the
post text is fired as a result of the mouse movement. Key next will not
fire unless there is a key event. The sequence of firing in a text item
are as follows ::
a) pre - text
b) when new item
c) key-next
d) when validate
e) post text
Can you store pictures in database? How?
Yes , in long Raw datatype.
What are property classes ? Can property classes have trigger?
Property class inheritance is a powerful
feature that allows you to quickly define objects that conform to your
own interface and functionality standards. Property classes also allow
you to make global changes to applications quickly. By simply changing
the definition of a property class, you can change the definition of all
objects that inherit properties from that class.
Yes . All type of triggers .
If you have property class attached to an item and you have same trigger written for the item . Which will fire first?
Item level trigger fires , If item level
trigger fires, property level trigger won't fire. Triggers at the lowest
level are always given the first preference. The item level trigger
fires first and then the block and then the Form level trigger.
What are record groups ? * Can record groups created at run-time?
A record group is an internal Oracle
Forms data structure that has a column/row framework similar to a
database table. However, unlike database tables, record groups are
separate objects that belong to the form module in which they are
defined. A record group can have an unlimited number of columns of type
CHAR, LONG, NUMBER, or DATE provided that the total number of columns
does not exceed 64K. Record group column names cannot exceed 30
characters.
Programmatically, record groups can be used whenever the
functionality offered by a two-dimensional array of multiple data types
is desirable.
TYPES OF RECORD GROUP:
Query Record Group A query record group is a record group that has
an associated SELECT statement. The columns in a query record group
derive their default names, data types, and lengths from the database
columns referenced in the SELECT statement. The records in a query
record group are the rows retrieved by the query associated with that
record group.
Non-query Record Group A non-query record group is a group that
does not have an associated query, but whose structure and values can be
modified programmatically at runtime.
Static Record Group A static record group is not associated with a
query; rather, you define its structure and row values at design time,
and they remain fixed at runtime.
What are ALERT?
An ALERT is a modal window that displays a message notifying operator of some application condition.
Can a button have icon and label at the same time ?
-NO
What is mouse navigate property of button?
When Mouse Navigate is True (the
default), Oracle Forms performs standard navigation to move the focus to
the item when the operator activates the item with the mouse.
When Mouse Navigate is set to False, Oracle Forms does not perform
navigation (and the resulting validation) to move to the item when an
operator activates the item with the mouse.
What is FORMS_MDI_WINDOW?
forms run inside the MDI application window. This property is useful for calling a form from another one.
What are timers ? when when-timer-expired does not fire?
The When-Timer-Expired trigger can not fire during trigger, navigation, or transaction processing.
Can object group have a block?
Yes , object group can have block as well as program units.
How many types of canvases are there.
There are 2 types of canvases called as
Content and Stack Canvas. Content canvas is the default and the one that
is used mostly for giving the base effect. Its like a plate on which we
add items and stacked canvas is used for giving 3 dimensional effect.
What are user-exits?
It invokes 3GL programs.
Can you pass values to-and-fro from foreign function ? how ?
Yes . You obtain a return value from a
foreign function by assigning the return value to an Oracle Forms
variable or item. Make sure that the Oracle Forms variable or item is
the same data type as the return value from the foreign function.
After assigning an Oracle Forms variable or item value to a PL/SQL
variable, pass the PL/SQL variable as a parameter value in the PL/SQL
interface of the foreign function. The PL/SQL variable that is passed as
a parameter must be a valid PL/SQL data type; it must also be the
appropriate parameter type as defined in the PL/SQL interface.
What is IAPXTB structure ?
The entries of Pro * C and user exits and the form which simulate the proc or user_exit are stored in IAPXTB table in d/b.
Can you call WIN-SDK thru user exits?
YES.
Does user exits supports DLL on MSWINDOWS ?
YES .
What is path setting for DLL?
Make sure you include the name of the DLL
in the FORMS45_USEREXIT variable of the ORACLE.INI file, or rename the
DLL to F45XTB.DLL. If you rename the DLL to F45XTB.DLL, replace the
existing F45XTB.DLL in the ORAWINBIN directory with the new F45XTB.DLL.
How is mapping of name of DLL and function done?
The dll can be created using the Visual
C++ / Visual Basic Tools and then the dll is put in the path that is
defined the registry.
What is precompiler?
It is similar to C precompiler directives.
Can you connect to non - oracle datasource ?
Yes .
What are key-mode and locking mode properties? level ?
Key Mode : Specifies how oracle forms
uniquely identifies rows in the database.This is property includes for
application that will run against NON-ORACLE datasources .
Key setting unique (default.)
dateable
n-updateable.
Locking mode :
Specifies when Oracle Forms should attempt to obtain database locks
on rows that correspond to queried records in the form. a) immediate b)
delayed
What are savepoint mode and cursor mode properties ? level?
Specifies whether Oracle Forms should
issue savepoints during a session. This property is included primarily
for applications that will run against non-ORACLE data sources. For
applications that will run against ORACLE, use the default setting.
Cursor mode - define cursor state across transaction Open/close.
What is transactional trigger property?
Identifies a block as transactional
control block. i.e. non - database block that oracle forms should manage
as transactional block.(NON-ORACLE datasource) default - FALSE.
What is OLE automation ?
OLE automation allows an OLE server
application to expose a set of commands and functions that can be
invoked from an OLE container application. OLE automation provides a way
for an OLE container application to use the features of an OLE server
application to manipulate an OLE object from the OLE container
environment. (FORMS_OLE)
What does invoke built-in do?
This procedure invokes a method.
Syntax:
PROCEDURE OLE2.INVOKE
(object obj_type,
method VARCHAR2,
list list_type := 0);
Parameters:
object Is an OLE2 Automation Object.
method Is a method (procedure) of the OLE2 object.
list Is the name of an argument list assigned to the OLE2.CREATE_ARGLIST function.
What are OPEN_FORM,CALL_FORM,NEW_FORM? diff?
CALL_FORM : It calls the other form. but
parent remains active, when called form completes the operation , it
releases lock and control goes back to the calling form.
When you call a form, Oracle Forms issues a savepoint for the
called form. If the CLEAR_FORM function causes a rollback when the
called form is current, Oracle Forms rolls back uncommitted changes to
this savepoint.
OPEN_FORM : When you call a form, Oracle Forms issues a savepoint
for the called form. If the CLEAR_FORM function causes a rollback when
the called form is current, Oracle Forms rolls back uncommitted changes
to this savepoint.
NEW_FORM : Exits the current form and enters the indicated form.
The calling form is terminated as the parent form. If the calling form
had been called by a higher form, Oracle Forms keeps the higher call
active and treats it as a call to the new form. Oracle Forms releases
memory (such as database cursors) that the terminated form was using.
Oracle Forms runs the new form with the same Runform options as the
parent form. If the parent form was a called form, Oracle Forms runs
the new form with the same options as the parent form.
What is call form stack?
When successive forms are loaded via the CALL_FORM procedure, the resulting module hierarchy is known as the call form stack.
Can u port applictions across the platforms? how?
Yes we can port applications across
platforms.Consider the form developed in a windows system.The form would
be generated in unix system by using f45gen my_form.fmb scott/tiger
What is a visual attribute?
Visual attributes are the font, color,
and pattern properties that you set for form and menu objects that
appear in your application's interface.
Diff. between VAT and Property Class?
Named visual attributes define only font,
color, and pattern attributes; property classes can contain these and
any other properties.
You can change the appearance of objects at runtime by changing the
named visual attribute programmatically; property class assignment
cannot be changed programmatically. When an object is inheriting from
both a property class and a named visual attribute, the named visual
attribute settings take precedence, and any visual attribute properties
in the class are ignored.
Which trigger related to mouse?
When-Mouse-Click
When-Mouse-DoubleClick
When-Mouse-Down
When-Mouse-Enter
When-Mouse-Leave
When-Mouse-Move
When-Mouse-Up
What is Current record attribute property?
Specifies the named visual attribute used
when an item is part of the current record. Current Record Attribute is
frequently used at the block level to display the current row in a
multi-record If you define an item-level Current Record Attribute, you
can display a pre-determined item in a special color when it is part of
the current record, but you cannot dynamically highlight the current
item, as the input focus changes.
Can u change VAT at run time?
Yes. You can programmatically change an
object's named visual attribute setting to change the font, color, and
pattern of the object at runtime.
Can u set default font in forms?
Yes. Change windows registry(regedit). Set form45_font to the desired font.
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What is Log Switch ?
The point at which ORACLE ends writing to one online redo log file and begins writing to another is called a log switch.
What is On-line Redo Log?
The On-line Redo Log is a set of tow or
more on-line redo files that record all committed changes made to the
database. Whenever a transaction is committed, the corresponding redo
entries temporarily stores in redo log buffers of the SGA are written to
an on-line redo log file by the background process LGWR. The on-line
redo log files are used in cyclical fashion.
Which parameter specified in the DEFAULT STORAGE clause of CREATE TABLESPACE cannot be altered after creating the tablespace?
All the default storage parameters
defined for the tablespace can be changed using the ALTER TABLESPACE
command. When objects are created their INITIAL and MINEXTENS values
cannot be changed.
What are the steps involved in Database Startup ?
Start an instance, Mount the Database and Open the Database.
Rolling forward to recover data that has not been recorded in data
files, yet has been recorded in the on-line redo log, including the
contents of rollback segments. Rolling back transactions that have been
explicitly rolled back or have not been committed as indicated by the
rollback segments regenerated in step a. Releasing any resources (locks)
held by transactions in process at the time of the failure. Resolving
any pending distributed transactions undergoing a two-phase commit at
the time of the instance failure.
Can Full Backup be performed when the database is open ?
No.
What are the different modes of mounting a Database with the Parallel Server ?
Exclusive Mode If the first instance that
mounts a database does so in exclusive mode, only that Instance can
mount the database.
Parallel Mode If the first instance that mounts a database is
started in parallel mode, other instances that are started in parallel
mode can also mount the database.
What are the advantages of operating a database in ARCHIVELOG mode over operating it in NO ARCHIVELOG mode ?
Complete database recovery from disk
failure is possible only in ARCHIVELOG mode. Online database backup is
possible only in ARCHIVELOG mode.
What are the steps involved in Database Shutdown ?
Close the Database, Dismount the Database and Shutdown the Instance.
What is Archived Redo Log ?
Archived Redo Log consists of Redo Log files that have archived before being reused.
What is Restricted Mode of Instance Startup ?
An instance can be started in (or later
altered to be in) restricted mode so that when the database is open
connections are limited only to those whose user accounts have been
granted the RESTRICTED SESSION system privilege.
Can u have OLE objects in forms?
Yes.
Can u have VBX and OCX controls in forms ?
Yes.
What r the types of windows (Window style)?
Specifies whether the window is a Document window or a Dialog window.
What is OLE Activation style property?
Specifies the event that will activate the OLE containing item.
Can u change the mouse pointer ? How?
Yes. Specifies the mouse cursor style. Use this property to dynamically change the shape of the cursor.
How many types of columns are there and what are they
Formula columns :: For doing mathematical
calculations and returning one value Summary Columns :: For doing
summary calculations such as summations etc. Place holder Columns ::
These columns are useful for storing the value in a variable
Can u have more than one layout in report
It is possible to have more than one layout in a report by using the additional layout option in the layout editor.
Can u run the report with out a parameter form
Yes it is possible to run the report without parameter form by setting the PARAM value to Null
What is the lock option in reports layout
By using the lock option we cannot move
the fields in the layout editor outside the frame. This is useful for
maintaining the fields .
What is Flex
Flex is the property of moving the related fields together by setting the flex property on
What are the minimum number of groups required for a matrix report
The minimum of groups required for a matrix report are 4 e -----
What is a Synonym ?
A synonym is an alias for a table, view, sequence or program unit.
What is a Sequence ?
A sequence generates a serial list of unique numbers for numerical columns of a database's tables.
What is a Segment ?
A segment is a set of extents allocated for a certain logical structure.
What is schema?
A schema is collection of database objects of a User.
Describe Referential Integrity ?
A rule defined on a column (or set of
columns) in one table that allows the insert or update of a row only if
the value for the column or set of columns (the dependent value) matches
a value in a column of a related table (the referenced value). It also
specifies the type of data manipulation allowed on referenced data and
the action to be performed on dependent data as a result of any action
on referenced data.
What is Hash Cluster ?
A row is stored in a hash cluster based
on the result of applying a hash function to the row's cluster key
value. All rows with the same hash key value are stores together on
disk.
What is a Private Synonyms ?
A Private Synonyms can be accessed only by the owner.
What is Database Link ?
A database link is a named object that describes a "path" from one database to another.
What is index cluster?
A cluster with an index on the cluster key.
What is hash cluster?
A row is stored in a hash cluster based
on the result of applying a hash function to the row's cluster key
value. All rows with the same hash key value are stores together on
disk.
When can hash cluster used?
Hash clusters are better choice when a
table is often queried with equality queries. For such queries the
specified cluster key value is hashed. The resulting hash key value
points directly to the area on disk that stores the specified rows.
When can hash cluster used?
Hash clusters are better choice when a
table is often queried with equality queries. For such queries the
specified cluster key value is hashed. The resulting hash key value
points directly to the area on disk that stores the specified rows.
What are the types of database links?
Private database link, public database link & network database link.
What is private database link?
Private database link is created on
behalf of a specific user. A private database link can be used only when
the owner of the link specifies a global object name in a SQL statement
or in the definition of the owner's views or procedures.
What is public database link?
Public database link is created for the
special user group PUBLIC. A public database link can be used when any
user in the associated database specifies a global object name in a SQL
statement or object definition.
What is network database link?
Network database link is created and
managed by a network domain service. A network database link can be used
when any user of any database in the network specifies a global object
name in a SQL statement or object definition.
What is data block?
Oracle database's data is stored in data
blocks. One data block corresponds to a specific number of bytes of
physical database space on disk.
How to define data block size?
A data block size is specified for each
Oracle database when the database is created. A database users and
allocated free database space in Oracle data blocks. Block size is
specified in init.ora file and cannot be changed latter.
What is row chaining?
In circumstances, all of the data for a
row in a table may not be able to fit in the same data block. When this
occurs, the data for the row is stored in a chain of data block (one or
more) reserved for that segment.
What is an extent?
An extent is a specific number of
contiguous data blocks, obtained in a single allocation and used to
store a specific type of information.
What are the different types of segments?
Data segment, index segment, rollback segment and temporary segment.
What is a data segment?
Each non-clustered table has a data
segment. All of the table's data is stored in the extents of its data
segment. Each cluster has a data segment. The data of every table in the
cluster is stored in the cluster's data segment.
What is an index segment?
Each index has an index segment that stores all of its data.
What is rollback segment?
A database contains one or more rollback segments to temporarily store "undo" information.
What are the uses of rollback segment?
To generate read-consistent database
information during database recovery and to rollback uncommitted
transactions by the users.
What is a temporary segment?
Temporary segments are created by Oracle
when a SQL statement needs a temporary work area to complete execution.
When the statement finishes execution, the temporary segment extents are
released to the system for future use.
What is a datafile?
Every Oracle database has one or more
physical data files. A database's data files contain all the database
data. The data of logical database structures such as tables and indexes
is physically stored in the data files allocated for a database.
What are the characteristics of data files?
A data file can be associated with only
one database. Once created a data file can't change size. One or more
data files form a logical unit of database storage called a tablespace.
What is a redo log?
The set of redo log files for a database is collectively known as the database redo log.
What is the function of redo log?
The primary function of the redo log is to record all changes made to data.
What is the use of redo log information?
The information in a redo log file is
used only to recover the database from a system or media failure
prevents database data from being written to a database's data files.
What does a control file contains?
- Database name
- Names and locations of a database's files and redolog files.
- Time stamp of database creation.
What is the use of control file?
When an instance of an Oracle database is
started, its control file is used to identify the database and redo log
files that must be opened for database operation to proceed. It is also
used in database recovery.
Is it possible to split the print reviewer into more than one region?
Yes
Is it possible to center an object horizontally in a repeating frame that has a variable horizontal size?
Yes
For a field in a repeating
frame, can the source come from the column which does not exist in the
data group which forms the base for the frame?
Yes
Can a field be used in a report without it appearing in any data group?
Yes
The join defined by the default data link is an outer join yes or no?
Yes
Can a formula column referred to columns in higher group?
Yes
Can a formula column be obtained through a select statement?
Yes
Is it possible to insert comments into sql statements return in the data model editor?
Yes
Is it possible to disable the parameter from while running the report?
Yes
When a form is invoked with call_form, Does oracle forms issues a save point?
Yes
Explain the difference between a hot backup and a cold backup and the benefits associated with each.
A hot backup is basically taking a backup
of the database while it is still up and running and it must be in
archive log mode. A cold backup is taking a backup of the database while
it is shut down and does not require being in archive log mode. The
benefit of taking a hot backup is that the database is still available
for use while the backup is occurring and you can recover the database
to any point in time. The benefit of taking a cold backup is that it is
typically easier to administer the backup and recovery process. In
addition, since you are taking cold backups the database does not
require being in archive log mode and thus there will be a slight
performance gain as the database is not cutting archive logs to disk.
You have just had to restore from backup and do not have any control files. How would you go about bringing up this database?
I would create a text based backup
control file, stipulating where on disk all the data files where and
then issue the recover command with the using backup control file
clause.
How do you switch from an init.ora file to a spfile?
Issue the create spfile from pfile command.
Explain the difference between a data block, an extent and a segment.
A data block is the smallest unit of
logical storage for a database object. As objects grow they take chunks
of additional storage that are composed of contiguous data blocks. These
groupings of contiguous data blocks are called extents. All the extents
that an object takes when grouped together are considered the segment
of the database object.
Give two examples of how you might determine the structure of the table DEPT.
Use the describe command or use the dbms_metadata.get_ddl package.
Where would you look for errors from the database engine?
In the alert log.
Compare and contrast TRUNCATE and DELETE for a table.
Both the truncate and delete command
have the desired outcome of getting rid of all the rows in a table. The
difference between the two is that the truncate command is a DDL
operation and just moves the high water mark and produces a now
rollback. The delete command, on the other hand, is a DML operation,
which will produce a rollback and thus take longer to complete.
Give the reasoning behind using an index.
Faster access to data blocks in a table.
Give the two types of tables involved in producing a star schema and the type of data they hold.
Fact tables and dimension tables. A fact
table contains measurements while dimension tables will contain data
that will help describe the fact tables.
What type of index should you use on a fact table?
A Bitmap index.
Give two examples of referential integrity constraints.
A primary key and a foreign key.
A table is classified as a
parent table and you want to drop and re-create it. How would you do
this without affecting the children tables?
Disable the foreign key constraint to the parent, drop the table, re-create the table, enable the foreign key constraint.
Explain the difference between ARCHIVELOG mode and NOARCHIVELOG mode and the benefits and disadvantages to each.
ARCHIVELOG mode is a mode that you can
put the database in for creating a backup of all transactions that have
occurred in the database so that you can recover to any point in time.
NOARCHIVELOG mode is basically the absence of ARCHIVELOG mode and has
the disadvantage of not being able to recover to any point in time.
NOARCHIVELOG mode does have the advantage of not having to write
transactions to an archive log and thus increases the performance of the
database slightly.
What command would you use to create a backup control file?
Alter database backup control file to trace.
Give the stages of instance startup to a usable state where normal users may access it.
STARTUP NOMOUNT - Instance startup
STARTUP MOUNT - The database is mounted
STARTUP OPEN - The database is opened
What column differentiates the V$ views to the GV$ views and how?
The INST_ID column which indicates the instance in a RAC environment the information came from.
How would you go about generating an EXPLAIN plan?
Create a plan table with utlxplan.sql.
Use the explain plan set statement_id = 'tst1' into plan_table for a SQL statement
Look at the explain plan with utlxplp.sql or utlxpls.sql
How would you go about increasing the buffer cache hit ratio?
Use the buffer cache advisory over a
given workload and then query the v$db_cache_advice table. If a change
was necessary then I would use the alter system set db_cache_size
command.
Explain an ORA-01555
You get this error when you get a
snapshot too old within rollback. It can usually be solved by increasing
the undo retention or increasing the size of rollbacks. You should also
look at the logic involved in the application getting the error
message.
Explain the difference between $ORACLE_HOME and $ORACLE_BASE.
ORACLE_BASE is the root directory for oracle. ORACLE_HOME located beneath ORACLE_BASE is where the oracle products reside.
How would you determine the time zone under which a database was operating?
select DBTIMEZONE from dual;
Explain the use of setting GLOBAL_NAMES equal to TRUE.
Setting GLOBAL_NAMES dictates how you
might connect to a database. This variable is either TRUE or FALSE and
if it is set to TRUE it enforces database links to have the same name as
the remote database to which they are linking.
What command would you use to encrypt a PL/SQL application?
WRAP
Explain the difference between a FUNCTION, PROCEDURE and PACKAGE.
A function and procedure are the same in
that they are intended to be a collection of PL/SQL code that carries a
single task. While a procedure does not have to return any values to the
calling application, a function will return a single value. A package
on the other hand is a collection of functions and procedures that are
grouped together based on their commonality to a business function or
application.
Explain the use of table functions.
Table functions are designed to return a
set of rows through PL/SQL logic but are intended to be used as a normal
table or view in a SQL statement. They are also used to pipeline
information in an ETL process.
Name three advisory statistics you can collect.
Buffer Cache Advice, Segment Level Statistics, & Timed Statistics
Where in the Oracle directory tree structure are audit traces placed?
In unix $ORACLE_HOME/rdbms/audit, in Windows the event viewer
Explain materialized views and how they are used.
Materialized views are objects that are
reduced sets of information that have been summarized, grouped, or
aggregated from base tables. They are typically used in data warehouse
or decision support systems.
When a user process fails, what background process cleans up after it?
PMON
What background process refreshes materialized views?
The Job Queue Processes.
How would you determine what sessions are connected and what resources they are waiting for?
Use of V$SESSION and V$SESSION_WAIT
Describe what redo logs are.
Redo logs are logical and physical
structures that are designed to hold all the changes made to a database
and are intended to aid in the recovery of a database.
How would you force a log switch?
ALTER SYSTEM SWITCH LOGFILE;
Give two methods you could use to determine what DDL changes have been made.
You could use Logminer or Streams
What does coalescing a tablespace do?
Coalescing is only valid for
dictionary-managed tablespaces and de-fragments space by combining
neighboring free extents into large single extents.
What is the difference between a TEMPORARY tablespace and a PERMANENT tablespace?
A temporary tablespace is used for
temporary objects such as sort structures while permanent tablespaces
are used to store those objects meant to be used as the true objects of
the database.
Name a tablespace automatically created when you create a database.
The SYSTEM tablespace.
When creating a user, what permissions must you grant to allow them to connect to the database?
Grant the CONNECT to the user.
How do you add a data file to a tablespace
ALTER TABLESPACE <tablespace_name> ADD DATAFILE <datafile_name> SIZE
How do you resize a data file?
ALTER DATABASE DATAFILE <datafile_name> RESIZE <new_size>;
What view would you use to look at the size of a data file?
DBA_DATA_FILES
What view would you use to determine free space in a tablespace?
DBA_FREE_SPACE
How would you determine who has added a row to a table?
Turn on fine grain auditing for the table.
How can you rebuild an index?
ALTER INDEX <index_name> REBUILD;
Explain what partitioning is and what its benefit is.
Partitioning is a method of taking large tables and indexes and splitting them into smaller, more manageable pieces.
You have just compiled a PL/SQL package but got errors, how would you view the errors?
SHOW ERRORS
How can you gather statistics on a table?
The ANALYZE command.
How can you enable a trace for a session?
Use the DBMS_SESSION.SET_SQL_TRACE or
Use ALTER SESSION SET SQL_TRACE = TRUE;
What is the difference between the SQL*Loader and IMPORT utilities?
These two Oracle utilities are used for
loading data into the database. The difference is that the import
utility relies on the data being produced by another Oracle utility
EXPORT while the SQL*Loader utility allows data to be loaded that has
been produced by other utilities from different data sources just so
long as it conforms to ASCII formatted or delimited files.
Name two files used for network connection to a database.
TNSNAMES.ORA and SQLNET.ORA
What is the function of Optimizer ?
The goal of the optimizer is to choose the most efficient way to execute a SQL statement.
What is Execution Plan ?
The combinations of the steps the optimizer chooses to execute a statement is called an execution plan.
Can one resize tablespaces and data files? (for DBA)
One can manually increase or decrease the size of a datafile from Oracle 7.2 using the command.
ALTER DATABASE DATAFILE 'filename2' RESIZE 100M;
Because you can change the sizes of datafiles, you can add more
space to your database without adding more datafiles. This is beneficial
if you are concerned about reaching the maximum number of datafiles
allowed in your database.
Manually reducing the sizes of datafiles allows you to reclaim
unused space in the database. This is useful for correcting errors in
estimations of space requirements.
Also, datafiles can be allowed to automatically extend if more space is required. Look at the following command:
CREATE TABLESPACE pcs_data_ts
DATAFILE 'c:\ora_apps\pcs\pcsdata1.dbf' SIZE 3M
AUTOEXTEND ON NEXT 1M MAXSIZE UNLIMITED
DEFAULT STORAGE (INITIAL 10240
NEXT 10240
MINEXTENTS 1
MAXEXTENTS UNLIMITED
PCTINCREASE 0)
ONLINE
PERMANENT;
What is SAVE POINT ?
For long transactions that contain many
SQL statements, intermediate markers or savepoints can be declared which
can be used to divide a transaction into smaller parts. This allows the
option of later rolling back all work performed from the current point
in the transaction to a declared savepoint within the transaction.
What are the values that can be specified for OPTIMIZER MODE Parameter ?
COST and RULE.
Can one rename a tablespace? (for DBA)
No, this is listed as Enhancement Request 148742. Workaround:
Export all of the objects from the tablespace
Drop the tablespace including contents
Recreate the tablespace
Import the objects
What is RULE-based approach to optimization ?
Choosing an executing planbased on the access paths available and the ranks of these access paths.
What are the values that can be specified for OPTIMIZER_GOAL parameter of the ALTER SESSION Command ?
CHOOSE,ALL_ROWS,FIRST_ROWS and RULE.
How does one create a standby database? (for DBA)
While your production database is
running, take an (image copy) backup and restore it on duplicate
hardware. Note that an export will not work!!!
On your standby database, issue the following commands:
ALTER DATABASE CREATE STANDBY CONTROLFILE AS 'filename';
ALTER DATABASE MOUNT STANDBY DATABASE;
RECOVER STANDBY DATABASE;
On systems prior to Oracle 8i, write a job to copy archived redo
log files from the primary database to the standby system, and apply the
redo log files to the standby database (pipe it). Remember the database
is recovering and will prompt you for the next log file to apply.
Oracle 8i onwards provide an "Automated Standby Database" feature,
which will send archived, log files to the remote site via NET8, and
apply then to the standby database.
When one needs to activate the standby database, stop the recovery process and activate it:
ALTER DATABASE ACTIVATE STANDBY DATABASE;
How does one give developers access to trace files (required as input to tkprof)? (for DBA)
The "alter session set sql_trace=true"
command generates trace files in USER_DUMP_DEST that can be used by
developers as input to tkprof. On Unix the default file mask for these
files are "rwx r-- ---".
There is an undocumented INIT.ORA parameter that will allow everyone to read (rwx r-r--) these trace files:
_trace_files_public = true
Include this in your INIT.ORA file and bounce your database for it to take effect.
What are the responsibilities of a Database Administrator ?
Installing and upgrading the Oracle
Server and application tools. Allocating system storage and planning
future storage requirements for the database system. Managing primary
database structures (tablespaces) Managing primary objects
(table,views,indexes) Enrolling users and maintaining system security.
Ensuring compliance with Oralce license agreement Controlling and
monitoring user access to the database. Monitoring and optimizing the
performance of the database. Planning for backup and recovery of
database information. Maintain archived data on tape Backing up and
restoring the database. Contacting Oracle Corporation for technical
support.
What is a trace file and how is it created ?
Each server and background process can
write an associated trace file. When an internal error is detected by a
process or user process, it dumps information about the error to its
trace. This can be used for tuning the database.
What are the roles and user accounts created automatically with the database?
DBA - role Contains all database system privileges.
SYS user account - The DBA role will be assigned to this account.
All of the base tables and views for the database's dictionary are store
in this schema and are manipulated only by ORACLE. SYSTEM user account -
It has all the system privileges for the database and additional tables
and views that display administrative information and internal tables
and views used by oracle tools are created using this username.
What are the minimum parameters should exist in the parameter file (init.ora) ?
DB NAME - Must set to a text string of no
more than 8 characters and it will be stored inside the datafiles, redo
log files and control files and control file while database creation.
DB_DOMAIN - It is string that specifies the network domain where
the database is created. The global database name is identified by
setting these parameters
(DB_NAME & DB_DOMAIN) CONTORL FILES - List of control filenames
of the database. If name is not mentioned then default name will be
used.
DB_BLOCK_BUFFERS - To determine the no of buffers in the buffer cache in SGA.
PROCESSES - To determine number of operating system processes that
can be connected to ORACLE concurrently. The value should be 5
(background process) and additional 1 for each user.
ROLLBACK_SEGMENTS - List of rollback segments an ORACLE instance
acquires at database startup. Also optionally
LICENSE_MAX_SESSIONS,LICENSE_SESSION_WARNING and LICENSE_MAX_USERS.
Why and when should I backup my database? (for DBA)
Backup and recovery is one of the most
important aspects of a DBAs job. If you lose your company's data, you
could very well lose your job. Hardware and software can always be
replaced, but your data may be irreplaceable!
Normally one would schedule a hierarchy of daily, weekly and
monthly backups, however consult with your users before deciding on a
backup schedule. Backup frequency normally depends on the following
factors:
. Rate of data change/ transaction rate
. Database availability/ Can you shutdown for cold backups?
. Criticality of the data/ Value of the data to the company
. Read-only tablespace needs backing up just once right after you make it read-only
. If you are running in archivelog mode you can backup parts of a database over an extended cycle of days
. If archive logging is enabled one needs to backup archived log files timeously to prevent database freezes
. Etc.
Carefully plan backup retention periods. Ensure enough backup media
(tapes) are available and that old backups are expired in-time to make
media available for new backups. Off-site vaulting is also highly
recommended.
Frequently test your ability to recover and document all possible
scenarios. Remember, it's the little things that will get you. Most
failed recoveries are a result of organizational errors and
miscommunications.
What strategies are available for backing-up an Oracle database? (for DBA)
The following methods are valid for backing-up an Oracle database:
Export/Import - Exports are "logical" database backups in that they
extract logical definitions and data from the database to a file.
Cold or Off-line Backups - Shut the database down and backup up ALL data, log, and control files.
Hot or On-line Backups - If the databases are available and in
ARCHIVELOG mode, set the tablespaces into backup mode and backup their
files. Also remember to backup the control files and archived redo log
files.
RMAN Backups - While the database is off-line or on-line, use the "rman" utility to backup the database.
It is advisable to use more than one of these methods to backup
your database. For example, if you choose to do on-line database
backups, also cover yourself by doing database exports. Also test ALL
backup and recovery scenarios carefully. It is better to be save than
sorry.
Regardless of your strategy, also remember to backup all required
software libraries, parameter files, password files, etc. If your
database is in ARCGIVELOG mode, you also need to backup archived log
files.
What is the difference between online and offline backups? (for DBA)
A hot backup is a backup performed while
the database is online and available for read/write. Except for Oracle
exports, one can only do on-line backups when running in ARCHIVELOG
mode.
A cold backup is a backup performed while the database is off-line and unavailable to its users.
What is the difference between restoring and recovering? (for DBA)
Restoring involves copying backup files
from secondary storage (backup media) to disk. This can be done to
replace damaged files or to copy/move a database to a new location.
Recovery is the process of applying redo logs to the database to
roll it forward. One can roll-forward until a specific point-in-time
(before the disaster occurred), or roll-forward until the last
transaction recorded in the log files. Sql> connect SYS as SYSDBA
Sql> RECOVER DATABASE UNTIL TIME '2001-03-06:16:00:00' USING BACKUP CONTROLFILE;
How does one backup a database using the export utility? (for DBA)
Oracle exports are "logical" database
backups (not physical) as they extract data and logical definitions from
the database into a file. Other backup strategies normally back-up the
physical data files.
One of the advantages of exports is that one can selectively
re-import tables, however one cannot roll-forward from an restored
export file. To completely restore a database from an export file one
practically needs to recreate the entire database.
Always do full system level exports (FULL=YES). Full exports
include more information about the database in the export file than user
level exports.
What are the built_ins used the display the LOV?
Show_lov
List_values
How do you call other Oracle Products from Oracle Forms?
Run_product is a built-in, Used to invoke
one of the supported oracle tools products and specifies the name of
the document or module to be run. If the called product is unavailable
at the time of the call, Oracle Forms returns a message to the operator.
What is the main diff. bet. Reports 2.0 & Reports 2.5?
Report 2.5 is object oriented.
What are the Built-ins to display the user-named editor?
A user named editor can be displayed
programmatically with the built in procedure SHOW-EDITOR, EDIT_TETITEM
independent of any particular text item.
How many number of columns a record group can have?
A record group can have an unlimited
number of columns of type CHAR, LONG, NUMBER, or DATE provided that the
total number of column does not exceed 64K.
What is a Query Record Group?
A query record group is a record group
that has an associated SELECT statement. The columns in a query record
group derive their default names, data types, had lengths from the
database columns referenced in the SELECT statement. The records in
query record group are the rows retrieved by the query associated with
that record group.
What does the term panel refer to with regard to pages?
A panel is the no. of physical pages needed to print one logical page.
What is a master detail relationship?
A master detail relationship is an
association between two base table blocks- a master block and a detail
block. The relationship between the blocks reflects a primary key to
foreign key relationship between the tables on which the blocks are
based.
What is a library?
A library is a collection of subprograms including user named procedures, functions and packages.
What is an anchoring object & what is its use? What are the various sub events a mouse double click event involves?
An anchoring object is a print condition object which used to explicitly or implicitly anchor other objects to itself.
Use the add_group_column function to add a column to record group that was created at a design time?
False
What are the various sub
events a mouse double click event involves? What are the various sub
events a mouse double click event involves?
Double clicking the mouse consists of the mouse down, mouse up, mouse click, mouse down & mouse up events.
What is the use of break group? What are the various sub events a mouse double click event involves?
A break group is used to display one record for one group ones. While multiple related records in other group can be displayed.
What tuning indicators can one use? (for DBA)
The following high-level tuning indicators can be used to establish if a database is performing optimally or not:
. Buffer Cache Hit Ratio
Formula: Hit Ratio = (Logical Reads - Physical Reads) / Logical Reads
Action: Increase DB_CACHE_SIZE (DB_BLOCK_BUFFERS prior to 9i) to increase hit ratio
. Library Cache Hit Ratio
Action: Increase the SHARED_POOL_SIZE to increase hit ratio
What tools/utilities does Oracle provide to assist with performance tuning? (for DBA)
Oracle provide the following tools/ utilities to assist with performance monitoring and tuning:
. TKProf
. UTLBSTAT.SQL and UTLESTAT.SQL - Begin and end stats monitoring
. Statspack
. Oracle Enterprise Manager - Tuning Pack
What is STATSPACK and how does one use it? (for DBA)
Statspack is a set of performance
monitoring and reporting utilities provided by Oracle from Oracle8i and
above. Statspack provides improved BSTAT/ESTAT functionality, though the
old BSTAT/ESTAT scripts are still available. For more information about
STATSPACK, read the documentation in file
$ORACLE_HOME/rdbms/admin/spdoc.txt.
Install Statspack:
cd $ORACLE_HOME/rdbms/admin
sqlplus "/ as sysdba" @spdrop.sql -- Install Statspack -
sqlplus "/ as sysdba" @spcreate.sql-- Enter tablespace names when prompted
Use Statspack:
sqlplus perfstat/perfstat
exec statspack.snap; -- Take a performance snapshots
exec statspack.snap;
o Get a list of snapshots
select SNAP_ID, SNAP_TIME from STATS$SNAPSHOT;
@spreport.sql -- Enter two snapshot id's for difference report
Other Statspack Scripts:
. sppurge.sql - Purge a range of Snapshot Id's between the specified begin and end Snap Id's
. spauto.sql - Schedule a dbms_job to automate the collection of STATPACK statistics
. spcreate.sql - Installs the STATSPACK user, tables and package on a database (Run as SYS).
. spdrop.sql - Deinstall STATSPACK from database (Run as SYS)
. sppurge.sql - Delete a range of Snapshot Id's from the database
. spreport.sql - Report on differences between values recorded in two snapshots
. sptrunc.sql - Truncates all data in Statspack tables
What are the common RMAN errors (with solutions)? (for DBA)
Some of the common RMAN errors are:
RMAN-20242: Specification does not match any archivelog in the recovery catalog.
Add to RMAN script: sql 'alter system archive log current';
RMAN-06089: archived log xyz not found or out of sync with catalog
Execute from RMAN: change archivelog all validate;
How can you execute the user defined triggers in forms 3.0 ?
Execute Trigger (trigger-name)
What ERASE package procedure does ?
Erase removes an indicated global variable.
What is the difference between NAME_IN and COPY ?
Copy is package procedure and writes values into a field.
Name in is a package function and returns the contents of the variable to which you apply.
What package procedure is used for calling another form ?
Call (E.g. Call(formname)
When the form is running in
DEBUG mode, If you want to examine the values of global variables and
other form variables, What package procedure command you would use in
your trigger text ?
Break.
SYSTEM VARIABLES
The value recorded in system.last_record variable is of type
a. Number
b. Boolean
c. Character. ?
b. Boolean.
What is mean by Program Global Area (PGA) ?
It is area in memory that is used by a Single Oracle User Process.
What is hit ratio ?
It is a measure of well the data cache
buffer is handling requests for data. Hit Ratio = (Logical Reads -
Physical Reads - Hits Misses)/ Logical Reads.
How do u implement the If statement in the Select Statement
We can implement the if statement in the
select statement by using the Decode statement. e.g. select DECODE
(EMP_CAT,'1','First','2','Second'Null); Here the Null is the else
statement where null is done .
How many types of Exceptions are there
There are 2 types of exceptions. They are
a) System Exceptions
e.g. When no_data_found, When too_many_rows
b) User Defined Exceptions
e.g. My_exception exception
When My_exception then
What are the inline and the precompiler directives
The inline and precompiler directives detect the values directly
How do you use the same lov for 2 columns
We can use the same lov for 2 columns by passing the return values in global values and using the global values in the code
How many minimum groups are required for a matrix report
The minimum number of groups in matrix report are 4
What is the difference between static and dynamic lov
The static lov contains the predetermined values while the dynamic lov contains values that come at run time
How does one manage Oracle database users? (for DBA)
Oracle user accounts can be locked,
unlocked, forced to choose new passwords, etc. For example, all accounts
except SYS and SYSTEM will be locked after creating an Oracle9iDB
database using the DB Configuration Assistant (dbca). DBA's must unlock
these accounts to make them available to users.
Look at these examples:
ALTER USER scott ACCOUNT LOCK -- lock a user account
ALTER USER scott ACCOUNT UNLOCK; -- unlocks a locked users account
ALTER USER scott PASSWORD EXPIRE; -- Force user to choose a new password
What is the difference between DBFile Sequential and Scattered Reads?(for DBA)
Both "db file sequential read" and "db
file scattered read" events signify time waited for I/O read requests to
complete. Time is reported in 100's of a second for Oracle 8i releases
and below, and 1000's of a second for Oracle 9i and above. Most people
confuse these events with each other as they think of how data is read
from disk. Instead they should think of how data is read into the SGA
buffer cache.
db file sequential read:
A sequential read operation reads data into contiguous memory
(usually a single-block read with p3=1, but can be multiple blocks).
Single block I/Os are usually the result of using indexes. This event is
also used for rebuilding the control file and reading data file headers
(P2=1). In general, this event is indicative of disk contention on
index reads.
db file scattered read:
Similar to db file sequential reads, except that the session is
reading multiple data blocks and scatters them into different
discontinuous buffers in the SGA. This statistic is NORMALLY indicating
disk contention on full table scans. Rarely, data from full table scans
could be fitted into a contiguous buffer area, these waits would then
show up as sequential reads instead of scattered reads.
The following query shows average wait time for sequential versus scattered reads:
prompt "AVERAGE WAIT TIME FOR READ REQUESTS"
select a.average_wait "SEQ READ", b.average_wait "SCAT READ"
from sys.v_$system_event a, sys.v_$system_event b
where a.event = 'db file sequential read'
and b.event = 'db file scattered read';
What is the use of PARFILE option in EXP command ?
Name of the parameter file to be passed for export.
What is the use of TABLES option in EXP command ?
List of tables should be exported.ze)
What is the OPTIMAL parameter?
It is used to set the optimal length of a rollback segment.
How does one use ORADEBUG from Server Manager/ SQL*Plus? (for DBA)
Execute the "ORADEBUG HELP" command from
svrmgrl or sqlplus to obtain a list of valid ORADEBUG commands. Look at
these examples:
SQLPLUS> REM Trace SQL statements with bind variables
SQLPLUS> oradebug setospid 10121
Oracle pid: 91, Unix process pid: 10121, image: oracleorcl
SQLPLUS> oradebug EVENT 10046 trace name context forever, level 12
Statement processed.
SQLPLUS> ! vi /app/oracle/admin/orcl/bdump/ora_10121.trc
SQLPLUS> REM Trace Process Statistics
SQLPLUS> oradebug setorapid 2
Unix process pid: 1436, image: ora_pmon_orcl
SQLPLUS> oradebug procstat
Statement processed.
SQLPLUS>> oradebug TRACEFILE_NAME
/app/oracle/admin/orcl/bdump/pmon_1436.trc
SQLPLUS> REM List semaphores and shared memory segments in use
SQLPLUS> oradebug ipc
SQLPLUS> REM Dump Error Stack
SQLPLUS> oradebug setospid <pid>
SQLPLUS> oradebug event immediate trace name errorstack level 3
SQLPLUS> REM Dump Parallel Server DLM locks
SQLPLUS> oradebug lkdebug -a convlock
SQLPLUS> oradebug lkdebug -a convres
SQLPLUS> oradebug lkdebug -r <resource handle> (i.e 0x8066d338 from convres dump)
Are there any undocumented commands in Oracle? (for DBA)
Sure there are, but it is hard to find them. Look at these examples:
From Server Manager (Oracle7.3 and above): ORADEBUG HELP
It looks like one can change memory locations with the ORADEBUG
POKE command. Anyone brave enough to test this one for us? Previously
this functionality was available with ORADBX (ls -l
$ORACLE_HOME/rdbms/lib/oradbx.o; make -f oracle.mk oradbx) SQL*Plus:
ALTER SESSION SET CURRENT_SCHEMA = SYS
If the maximum record retrieved property of the query is set to 10 then a summary value will be calculated?
Only for 10 records.
What are the different objects that you cannot copy or reference in object groups?
Objects of different modules
Another object groups
Individual block dependent items
Program units.
What is an OLE?
Object Linking & Embedding provides
you with the capability to integrate objects from many Ms-Windows
applications into a single compound document creating integrated
applications enables you to use the features form .
Can a repeating frame be created without a data group as a base?
No
Is it possible to set a filter condition in a cross product group in matrix reports?
No
What is Overloading of procedures ?
The Same procedure name is repeated with
parameters of different datatypes and parameters in different positions,
varying number of parameters is called overloading of procedures. e.g.
DBMS_OUTPUT put_line
What are the return values of functions SQLCODE and SQLERRM ? What is Pragma EXECPTION_INIT ? Explain the usage ?
SQLCODE returns the latest code of the error that has occurred.
SQLERRM returns the relevant error message of the SQLCODE.
What are the datatypes a available in PL/SQL ?
Some scalar data types such as NUMBER,
VARCHAR2, DATE, CHAR, LONG, BOOLEAN. Some composite data types such as
RECORD & TABLE.
What are the two parts of a procedure ?
Procedure Specification and Procedure Body.
What is the basic structure of PL/SQL ?
PL/SQL uses block structure as its basic structure. Anonymous blocks or nested blocks can be used in PL/SQL
What is PL/SQL table ?
Objects of type TABLE are called "PL/SQL
tables", which are modeled as (but not the same as) database tables,
PL/SQL tables use a primary PL/SQL tables can have one column and a
primary key. Cursors
WHAT IS RMAN ? (for DBA)
Recovery Manager is a tool that: manages
the process of creating backups and also manages the process of
restoring and recovering from them.
WHY USE RMAN ? (for DBA)
No extra costs …Its available free
?RMAN introduced in Oracle 8 it has become simpler with newer versions and easier than user managed backups
?Proper security
?You are 100% sure your database has been backed up.
?Its contains detail of the backups taken etc in its central repository
Facility for testing validity of backups also commands like crosscheck to check the status of backup.
Faster backups and restores compared to backups without RMAN
RMAN is the only backup tool which supports incremental backups.
Oracle 10g has got further optimized incremental backup which has
resulted in improvement of performance during backup and recovery time
Parallel operations are supported
Better querying facility for knowing different details of backup
No extra redo generated when backup is taken..compared to online
backup without RMAN which results in saving of space in hard disk
RMAN an intelligent tool
Maintains repository of backup metadata
Remembers backup set location
Knows what need to backed up
Knows what is required for recovery
Knows what backups are redundant
UNDERSTANDING THE RMAN ARCHITECTURE
An oracle RMAN comprises of
RMAN EXECUTABLE This could be present and fired even through client side
TARGET DATABASE This is the database which needs to be backed up .
RECOVERY CATALOG Recovery catalog is optional otherwise backup details are stored in target database controlfile .
It is a repository of information queried and updated by Recovery Manager
It is a schema or user stored in Oracle database. One schema can support many databases
It contains information about physical schema of target database
datafile and archive log ,backup sets and pieces Recovery catalog is a
must in following scenarios
. In order to store scripts
. For tablespace point in time recovery
Media Management Software
Media Management software is a must if you are using RMAN for storing backup in tape drive directly.
Backups in RMAN
Oracle backups in RMAN are of the following type
RMAN complete backup OR RMAN incremental backup
These backups are of RMAN proprietary nature
IMAGE COPY
The advantage of uing Image copy is its not in RMAN proprietary format..
Backup Format
RMAN backup is not in oracle format but in RMAN format. Oracle
backup comprises of backup sets and it consists of backup pieces. Backup
sets are logical entity In oracle 9i it gets stored in a default
location There are two type of backup sets Datafile backup sets,
Archivelog backup sets One more important point of data file backup sets
is it do not include empty blocks. A backup set would contain many
backup pieces.
A single backup piece consists of physical files which are in RMAN proprietary format.
Example of taking backup using RMAN
Taking RMAN Backup
In non archive mode in dos prompt type
RMAN
You get the RMAN prompt
RMAN > Connect Target
Connect to target database : Magic
using target database controlfile instead of recovery catalog
Lets take a simple backup of database in non archive mode
shutdown immediate ; - - Shutdowns the database
startup mount
backup database ;- its start backing the database
alter database open;
We can fire the same command in archive log mode
And whole of datafiles will be backed
Backup database plus archivelog;
Restoring database
Restoring database has been made very simple in 9i .
It is just
Restore database..
RMAN has become intelligent to identify which datafiles has to be restored
and the location of backuped up file.
Oracle Enhancement for RMAN in 10 G
Flash Recovery Area
Right now the price of hard disk is falling. Many dba are taking
oracle database backup inside the hard disk itself since it results in
lesser mean time between recoverability.
The new parameter introduced is
DB_RECOVERY_FILE_DEST = /oracle/flash_recovery_area
By configuring the RMAN RETENTION POLICY the flash recovery area
will automatically delete obsolete backups and archive logs that are no
longer required based on that configuration Oracle has introduced new
features in incremental backup
Change Tracking File
Oracle 10g has the facility to deliver faster incrementals with the
implementation of changed tracking file feature.This will results in
faster backups lesser space consumption and also reduces the time needed
for daily backups
Incrementally Updated Backups
Oracle database 10g Incrementally Updates Backup features merges
the image copy of a datafile with RMAN incremental backup. The resulting
image copy is now updated with block changes captured by incremental
backups.The merging of the image copy and incremental backup is
initiated with RMAN recover command. This results in faster recovery.
Binary compression technique reduces backup space usage by 50-75%.
With the new DURATION option for the RMAN BACKUP command, DBAs can
weigh backup performance against system service level requirements. By
specifying a duration, RMAN will automatically calculate the appropriate
backup rate; in addition, DBAs can optionally specify whether backups
should minimize time or system load.
New Features in Oem to identify RMAN related backup like backup pieces, backup sets and image copy
Oracle 9i New features Persistent RMAN Configuration
A new configure command has been introduced in Oracle 9i , that
lets you configure various features including automatic channels,
parallelism ,backup options, etc.
These automatic allocations and options can be overridden by commands in a RMAN command file.
Controlfile Auto backups
Through this new feature RMAN will automatically perform a controlfile auto backup. after every backup or copy command.
Block Media Recovery
If we can restore a few blocks rather than an entire file we only need few blocks.
We even dont need to bring the data file offline.
Syntax for it as follows
Block Recover datafile 8 block 22;
Configure Backup Optimization
Prior to 9i whenever we backed up database using RMAN our backup
also used take backup of read only table spaces which had already been
backed up and also the same with archive log too.
Now with 9i backup optimization parameter we can prevent repeat
backup of read only tablespace and archive log. The command for this is
as follows Configure backup optimization on
Archive Log failover
If RMAN cannot read a block in an archived log from a destination.
RMAN automatically attempts to read from an alternate location this is
called as archive log failover
There are additional commands like
backup database not backed up since time '31-jan-2002 14:00:00'
Do not backup previously backed up files
(say a previous backup failed and you want to restart from where it left off).
Similar syntax is supported for restores
backup device sbt backup set all Copy a disk backup to tape
(backing up a backup
Additionally it supports
. Backup of server parameter file
. Parallel operation supported
. Extensive reporting available
. Scripting
. Duplex backup sets
. Corrupt block detection
. Backup archive logs
Pitfalls of using RMAN
Previous to version Oracle 9i backups were not that easy which
means you had to allocate a channel compulsorily to take backup You had
to give a run etc . The syntax was a bit complex …RMAN has now become
very simple and easy to use..
If you changed the location of backup set it is compulsory for you
to register it using RMAN or while you are trying to restore backup It
resulted in hanging situations
There is no method to know whether during recovery database restore is going to fail because of missing archive log file.
Compulsory Media Management only if using tape backup
Incremental backups though used to consume less space used to be
slower since it used to read the entire database to find the changed
blocks and also They have difficult time streaming the tape device. .
Considerable improvement has been made in 10g to optimize the algorithm to handle changed block.
Observation
Introduced in Oracle 8 it has become more powerful and simpler with newer version of Oracle 9 and 10 g.
So if you really don't want to miss something critical please start using RMAN.
Explain UNION,MINUS,UNION ALL, INTERSECT ?
INTERSECT returns all distinct rows
selected by both queries.MINUS - returns all distinct rows selected by
the first query but not by the second.UNION - returns all distinct rows
selected by either queryUNION ALL - returns all rows selected by either
query, including all duplicates.
Should the OEM Console be displayed at all times (when there are scheduled jobs)? (for DBA)
When a job is submitted the agent will
confirm the status of the job. When the status shows up as scheduled,
you can close down the OEM console. The processing of the job is managed
by the OIA (Oracle Intelligent Agent). The OIA maintains a .jou file in
the agent's subdirectory. When the console is launched communication
with the Agent is established and the contents of the .jou file (binary)
are reported to the console job subsystem. Note that OEM will not be
able to send e-mail and paging notifications when the Console is not
started.
Difference between SUBSTR and INSTR ?
INSTR (String1,String2(n,(m)),INSTR
returns the position of the mth occurrence of the string 2 instring1.
The search begins from nth position of string1.SUBSTR (String1
n,m)SUBSTR returns a character string of size m in string1, starting
from nth position of string1.
What kind of jobs can one schedule with OEM? (for DBA)
OEM comes with pre-defined jobs like
Export, Import, run OS commands, run sql scripts, SQL*Plus commands etc.
It also gives you the flexibility of scheduling custom jobs written
with the TCL language.
What are the pre requisites ?
I. to modify data type of a column ? ii.
to add a column with NOT NULL constraint ? To Modify the datatype of a
column the column must be empty. to add a column with NOT NULL
constrain, the table must be empty.
How does one backout events and jobs during maintenance slots? (for DBA)
Managemnet and data collection activity can be suspended by imposing a blackout. Look at these examples:
agentctl start blackout # Blackout the entrire agent
agentctl stop blackout # Resume normal monitoring and management
agentctl start blackout ORCL # Blackout database ORCL
agentctl stop blackout ORCL # Resume normal monitoring and management
agentctl start blackout -s jobs -d 00:20 # Blackout jobs for 20 minutes
What are the types of SQL Statement ?
Data Definition Language :
CREATE,ALTER,DROP,TRUNCATE,REVOKE,NO AUDIT & COMMIT.
Data Manipulation Language:
INSERT,UPDATE,DELETE,LOCK
TABLE,EXPLAIN PLAN & SELECT.Transactional Control:
COMMIT & ROLLBACKSession Control: ALTERSESSION & SET
ROLESystem Control :
ALTER SYSTEM.
What is the Oracle Intelligent Agent? (for DBA)
The Oracle Intelligent Agent (OIA) is an
autonomous process that needs to run on a remote node in the network to
make the node OEM manageable. The Oracle Intelligent Agent is
responsible for:
. Discovering targets that can be managed (Database Servers, Net8 Listeners, etc.);
. Monitoring of events registered in Enterprise Manager; and
. Executing tasks associated with jobs submitted to Enterprise Manager.
How does one start the Oracle Intelligent Agent? (for DBA)
One needs to start an OIA (Oracle Intelligent Agent) process on all machines that will to be managed via OEM.
For OEM 9i and above:
agentctl start agent
agentctl stop agent
For OEM 2.1 and below:
lsnrctl dbsnmp_start
lsnrctl dbsnmp_status
On Windows NT, start the "OracleAgent" Service.
If the agent doesn't want to start, ensure your environment
variables are set correctly and delete the following files before trying
again:
1) In $ORACLE_HOME/network/admin: snmp_ro.ora and snmp_rw.ora.
2) Also delete ALL files in $ORACLE_HOME/network/agent/.
Can one write scripts to send alert messages to the console?
Start the OEM console and create a new
event. Select option "Enable Unsolicited Event". Select test
"Unsolicited Event". When entering the parameters, enter values similar
to these:
Event Name: /oracle/script/myalert
Object: *
Severity: *
Message: *
One can now write the script and invoke the oemevent command to
send alerts to the console. Look at this example: oemevent
/oracle/script/myalert DESTINATION alert "My custom error message" where
DESTINATION is the same value as entered in the "Monitored
Destinations" field when you've registered the event in the OEM Console.
Where can one get more information about TCL? (for DBA)
One can write custom event checking
routines for OEM using the TCL (Tool Command Language) language. Check
the following sites for more information about TCL:
. The Tcl Developer Xchange - download and learn about TCL
. OraTCL at Sourceforge - Download the OraTCL package
. Tom Poindexter's Tcl Page - Oratcl was originally written by Tom Poindexter
Are there any troubleshooting tips for OEM? (for DBA)
. Create the OEM repository with a user
(which will manage the OEM) and store it in a tablespace that does not
share any data with other database users. It is a bad practice to create
the repository with SYS and System.
. If you are unable to launch the console or there is a
communication problem with the intelligent agent (daemon). Ensure OCX
files are registered. Type the following in the DOS prompt (the current
directory should be $ORACLE_HOME\BIN:
C:\Orawin95\Bin> RegSvr32 mmdx32.OCX
C:\Orawin95\Bin> RegSvr32 vojt.OCX
. If you have a problem starting the Oracle Agent
Solution A: Backup the *.Q files and Delete all the *.Q Files ($Oracle_home/network/agent folder)
Backup and delete SNMP_RO.ora, SNMP_RW.ora, dbsnmp.ver and
services.ora files ($Oracle_Home/network/admin folder) Start the Oracle
Agent service.
Solution B: Your version of Intelligent Agent could be buggy. Check
with Oracle for any available patches. For example, the Intelligent
Agent that comes with Oracle 8.0.4 is buggy.
Sometimes you get a Failed status for the job that was executed successfully.
Check the log to see the results of the execution rather than relying on this status.
What is import/export and why does one need it? (for DBA)
The Oracle export (EXP) and import (IMP)
utilities are used to perform logical database backup and recovery. They
are also used to move Oracle data from one machine, database or schema
to another.
The imp/exp utilities use an Oracle proprietary binary file format
and can thus only be used between Oracle databases. One cannot export
data and expect to import it into a non-Oracle database. For more
information on how to load and unload data from files, read the
SQL*Loader FAQ.
The export/import utilities are also commonly used to perform the following tasks:
. Backup and recovery (small databases only)
. Reorganization of data/ Eliminate database fragmentation
. Detect database corruption. Ensure that all the data can be read.
. Transporting tablespaces between databases
. Etc.
What is a display item?
Display items are similar to text items
but store only fetched or assigned values. Operators cannot navigate to a
display item or edit the value it contains.
How does one use the import/export utilities? (for DBA)
Look for the "imp" and "exp" executables
in your $ORACLE_HOME/bin directory. One can run them interactively,
using command line parameters, or using parameter files. Look at the
imp/exp parameters before starting. These parameters can be listed by
executing the following commands: "exp help=yes" or "imp help=yes".
The following examples demonstrate how the imp/exp utilities can be used:
exp scott/tiger file=emp.dmp log=emp.log tables=emp rows=yes indexes=no
exp scott/tiger file=emp.dmp tables=(emp,dept)
imp scott/tiger file=emp.dmp full=yes
imp scott/tiger file=emp.dmp fromuser=scott touser=scott tables=dept
exp userid=scott/tiger@orcl parfile=export.txt
... where export.txt contains:
BUFFER=100000
FILE=account.dmp
FULL=n
OWNER=scott
GRANTS=y
COMPRESS=y
NOTE: If you do not like command line utilities, you can import and
export data with the "Schema Manager" GUI that ships with Oracle
Enterprise Manager (OEM).
What are the types of visual attribute settings?
Custom Visual attributes Default visual attributes Named Visual attributes. Window
Can one export a subset of a table? (for DBA)
From Oracle8i one can use the QUERY=
export parameter to selectively unload a subset of the data from a
table. Look at this example:
exp scott/tiger tables=emp query=\"where deptno=10\"
What are the two ways to incorporate images into a oracle forms application?
Boilerplate Images
Image_items
Can one monitor how fast a table is imported? (for DBA)
If you need to monitor how fast rows are imported from a running import job, try one of the following methods:
Method 1:
select substr(sql_text,instr(sql_text,'INTO "'),30) table_name,
rows_processed,
round((sysdate-to_date(first_load_time,'yyyy-mm-dd hh24:mi:ss'))*24*60,1) minutes,
trunc(rows_processed/((sysdate-to_date(first_load_time,'yyyy-mm-dd hh24:mi:ss'))*24*60)) rows_per_min
from sys.v_$sqlarea
where sql_text like 'INSERT %INTO "%'
and command_type = 2
and open_versions > 0;
For this to work one needs to be on Oracle 7.3 or higher (7.2 might
also be OK). If the import has more than one table, this statement will
only show information about the current table being imported.
Contributed by Osvaldo Ancarola, Bs. As. Argentina.
Method 2:
Use the FEEDBACK=n import parameter. This command will tell IMP to display a dot for every N rows imported.
Can one import tables to a different tablespace? (for DBA)
Oracle offers no parameter to specify a
different tablespace to import data into. Objects will be re-created in
the tablespace they were originally exported from. One can alter this
behaviour by following one of these procedures: Pre-create the table(s)
in the correct tablespace:
. Import the dump file using the INDEXFILE= option
. Edit the indexfile. Remove remarks and specify the correct tablespaces.
. Run this indexfile against your database, this will create the required tables in the appropriate tablespaces
. Import the table(s) with the IGNORE=Y option.
Change the default tablespace for the user:
. Revoke the "UNLIMITED TABLESPACE" privilege from the user
. Revoke the user's quota from the tablespace from where the object
was exported. This forces the import utility to create tables in the
user's default tablespace.
. Make the tablespace to which you want to import the default tablespace for the user
. Import the table
What do you mean by a block in forms4.0?
Block is a single mechanism for grouping related items into a functional unit for storing, displaying and manipulating records.
How is possible to restrict the user to a list of values while entering values for parameters?
By setting the Restrict To List property to true in the parameter property sheet.
What is SQL*Loader and what is it used for? (for DBA)
SQL*Loader is a bulk loader utility used
for moving data from external files into the Oracle database. Its syntax
is similar to that of the DB2 Load utility, but comes with more
options. SQL*Loader supports various load formats, selective loading,
and multi-table loads.
How does one use the SQL*Loader utility? (for DBA)
One can load data into an Oracle database
by using the sqlldr (sqlload on some platforms) utility. Invoke the
utility without arguments to get a list of available parameters. Look at
the following example:
sqlldr scott/tiger control=loader.ctl
This sample control file (loader.ctl) will load an external data file containing delimited data:
load data
infile 'c:\data\mydata.csv'
into table emp
fields terminated by "," optionally enclosed by '"'
( empno, empname, sal, deptno )
The mydata.csv file may look like this:
10001,"Scott Tiger", 1000, 40
10002,"Frank Naude", 500, 20
Another Sample control file with in-line data formatted as fix
length records. The trick is to specify "*" as the name of the data
file, and use BEGINDATA to start the data section in the control file.
load data
infile *
replace
into table departments
( dept position (02:05) char(4),
deptname position (08:27) char(20)
)
begindata
COSC COMPUTER SCIENCE
ENGL ENGLISH LITERATURE
MATH MATHEMATICS
POLY POLITICAL SCIENCE
How can a cross product be created?
By selecting the cross products tool and drawing a new group surrounding the base group of the cross products.
Is there a SQL*Unloader to download data to a flat file? (for DBA)
Oracle does not supply any data unload
utilities. However, you can use SQL*Plus to select and format your data
and then spool it to a file:
set echo off newpage 0 space 0 pagesize 0 feed off head off trimspool on
spool oradata.txt
select col1 || ',' || col2 || ',' || col3
from tab1
where col2 = 'XYZ';
spool off
Alternatively use the UTL_FILE PL/SQL package:
rem Remember to update initSID.ora, utl_file_dir='c:\oradata' parameter
declare
fp utl_file.file_type;
begin
fp := utl_file.fopen('c:\oradata','tab1.txt','w');
utl_file.putf(fp, '%s, %s\n', 'TextField', 55);
utl_file.fclose(fp);
end;
/
You might also want to investigate third party tools like SQLWays
from Ispirer Systems, TOAD from Quest, or ManageIT Fast Unloader from CA
to help you unload data from Oracle.
Can one load variable and fix length data records? (for DBA)
Yes, look at the following control file examples. In the first we will load delimited data (variable length):
LOAD DATA
INFILE *
INTO TABLE load_delimited_data
FIELDS TERMINATED BY "," OPTIONALLY ENCLOSED BY '"'
TRAILING NULLCOLS
( data1,
data2
)
BEGINDATA
11111,AAAAAAAAAA
22222,"A,B,C,D,"
If you need to load positional data (fixed length), look at the following control file example:
LOAD DATA
INFILE *
INTO TABLE load_positional_data
( data1 POSITION(1:5),
data2 POSITION(6:15)
)
BEGINDATA
11111AAAAAAAAAA
22222BBBBBBBBBB
Can one skip header records load while loading?
Use the "SKIP n" keyword, where n = number of logical rows to skip. Look at this example:
LOAD DATA
INFILE *
INTO TABLE load_positional_data
SKIP 5
( data1 POSITION(1:5),
data2 POSITION(6:15)
)
BEGINDATA
11111AAAAAAAAAA
22222BBBBBBBBBB
Can one modify data as it loads into the database? (for DBA)
Data can be modified as it loads into the
Oracle Database. Note that this only applies for the conventional load
path and not for direct path loads.
LOAD DATA
INFILE *
INTO TABLE modified_data
( rec_no "my_db_sequence.nextval",
region CONSTANT '31',
time_loaded "to_char(SYSDATE, 'HH24:MI')",
data1 POSITION(1:5) ":data1/100",
data2 POSITION(6:15) "upper(:data2)",
data3 POSITION(16:22)"to_date(:data3, 'YYMMDD')"
)
BEGINDATA
11111AAAAAAAAAA991201
22222BBBBBBBBBB990112
LOAD DATA
INFILE 'mail_orders.txt'
BADFILE 'bad_orders.txt'
APPEND
INTO TABLE mailing_list
FIELDS TERMINATED BY ","
( addr,
city,
state,
zipcode,
mailing_addr "decode(:mailing_addr, null, :addr, :mailing_addr)",
mailing_city "decode(:mailing_city, null, :city, :mailing_city)",
mailing_state
)
Can one load data into multiple tables at once? (for DBA)
Look at the following control file:
LOAD DATA
INFILE *
REPLACE
INTO TABLE emp
WHEN empno != ' '
( empno POSITION(1:4) INTEGER EXTERNAL,
ename POSITION(6:15) CHAR,
deptno POSITION(17:18) CHAR,
mgr POSITION(20:23) INTEGER EXTERNAL
)
INTO TABLE proj
WHEN projno != ' '
( projno POSITION(25:27) INTEGER EXTERNAL,
empno POSITION(1:4) INTEGER EXTERNAL
)
What is the difference between boiler plat images and image items?
Boiler plate Images are static images
(Either vector or bit map) that you import from the file system or
database to use a graphical elements in your form, such as company logos
and maps. Image items are special types of interface controls that
store and display either vector or bitmap images. Like other items that
store values, image items can be either base table items(items that
relate directly to database columns) or control items. The definition of
an image item is stored as part of the form module FMB and FMX files,
but no image file is actually associated with an image item until the
item is populate at run time.
hat are the triggers available in the reports?
Before report, Before form, After form , Between page, After report.
Why is a Where clause faster than a group filter or a format trigger?
Because, in a where clause the condition is applied during data retrievalthan after retrieving the data.
Can one selectively load only the records that one need? (for DBA)
Look at this example, (01) is the first character, (30:37) are characters 30 to 37:
LOAD DATA
INFILE 'mydata.dat' BADFILE 'mydata.bad' DISCARDFILE 'mydata.dis'
APPEND
INTO TABLE my_selective_table
WHEN (01) <> 'H' and (01) <> 'T' and (30:37) = '19991217'
(
region CONSTANT '31',
service_key POSITION(01:11) INTEGER EXTERNAL,
call_b_no POSITION(12:29) CHAR
)
Can one skip certain columns while loading data? (for DBA)
One cannot use POSTION(x:y) with
delimited data. Luckily, from Oracle 8i one can specify FILLER columns.
FILLER columns are used to skip columns/fields in the load file,
ignoring fields that one does not want. Look at this example: -- One
cannot use POSTION(x:y) as it is stream data, there are no positional
fields-the next field begins after some delimiter, not in column X.
-->
LOAD DATA
TRUNCATE INTO TABLE T1
FIELDS TERMINATED BY ','
( field1,
field2 FILLER,
field3
)
How does one load multi-line records? (for DBA)
One can create one logical record from multiple physical records using one of the following two clauses:
. CONCATENATE: - use when SQL*Loader should combine the same number of physical records together to form one logical record.
. CONTINUEIF - use if a condition indicates that multiple records
should be treated as one. Eg. by having a '#' character in column 1.
How can get SQL*Loader to COMMIT only at the end of the load file? (for DBA)
One cannot, but by setting the ROWS=
parameter to a large value, committing can be reduced. Make sure you
have big rollback segments ready when you use a high value for ROWS=.
Can one improve the performance of SQL*Loader? (for DBA)
A very simple but easily overlooked hint
is not to have any indexes and/or constraints (primary key) on your load
tables during the load process. This will significantly slow down load
times even with ROWS= set to a high value.
Add the following option in the command line: DIRECT=TRUE. This
will effectively bypass most of the RDBMS processing. However, there are
cases when you can't use direct load. Refer to chapter 8 on Oracle
server Utilities manual.
Turn off database logging by specifying the UNRECOVERABLE option.
This option can only be used with direct data loads. Run multiple load
jobs concurrently.
How does one use SQL*Loader to load images, sound clips and documents? (for DBA)
SQL*Loader can load data from a "primary
data file", SDF (Secondary Data file - for loading nested tables and
VARRAYs) or LOGFILE. The LOBFILE method provides and easy way to load
documents, images and audio clips into BLOB and CLOB columns. Look at
this example:
Given the following table:
CREATE TABLE image_table (
image_id NUMBER(5),
file_name VARCHAR2(30),
image_data BLOB);
Control File:
LOAD DATA
INFILE *
INTO TABLE image_table
REPLACE
FIELDS TERMINATED BY ','
(
image_id INTEGER(5),
file_name CHAR(30),
image_data LOBFILE (file_name) TERMINATED BY EOF
)
BEGINDATA
001,image1.gif
002,image2.jpg
What is the difference between the conventional and direct path loader? (for DBA)
The conventional path loader essentially
loads the data by using standard INSERT statements. The direct path
loader (DIRECT=TRUE) bypasses much of the logic involved with that, and
loads directly into the Oracle data files. More information about the
restrictions of direct path loading can be obtained from the Utilities
Users Guide.
GENERAL INTERVIEW QUESTIONS
What are the various types of Exceptions ?
User defined and Predefined Exceptions.
Can we define exceptions twice in same block ?
No.
What is the difference between a procedure and a function ?
Functions return a single variable by
value whereas procedures do not return any variable by value. Rather
they return multiple variables by passing variables by reference through
their OUT parameter.
Can you have two functions with the same name in a PL/SQL block ?
Yes.
Can you have two stored functions with the same name ?
Yes.
Can you call a stored function in the constraint of a table ?
No.
What are the various types of parameter modes in a procedure ?
IN, OUT AND INOUT.
What is Over Loading and what are its restrictions ?
OverLoading means an object performing
different functions depending upon the no. of parameters or the data
type of the parameters passed to it.
Can functions be overloaded ?
Yes.
Can 2 functions have same name & input parameters but differ only by return datatype ?
No.
What are the constructs of a procedure, function or a package ?
The constructs of a procedure, function or a package are :
variables and constants
cursors
exceptions
Why Create or Replace and not Drop and recreate procedures ?
So that Grants are not dropped.
Can you pass parameters in packages ? How ?
Yes. You can pass parameters to procedures or functions in a package.
What are the parts of a database trigger ?
The parts of a trigger are:
A triggering event or statement
A trigger restriction
A trigger action
What are the various types of database triggers ?
There are 12 types of triggers, they are combination of :
Insert, Delete and Update Triggers.
Before and After Triggers.
Row and Statement Triggers.
(3*2*2=12)
What is the advantage of a stored procedure over a database trigger ?
We have control over the firing of a stored procedure but we have no control over the firing of a trigger.
What is the maximum no. of statements that can be specified in a trigger statement ?
One.
Can views be specified in a trigger statement ?
No
What are the values of :new and :old in Insert/Delete/Update Triggers ?
INSERT : new = new value, old = NULL
DELETE : new = NULL, old = old value
UPDATE : new = new value, old = old value
What are cascading triggers? What is the maximum no of cascading triggers at a time?
When a statement in a trigger body causes another trigger to be fired, the triggers are said to be cascading. Max = 32.
What are mutating triggers ?
A trigger giving a SELECT on the table on which the trigger is written.
What are constraining triggers ?
A trigger giving an Insert/Update on a table having referential integrity constraint on the triggering table.
Describe Oracle database's physical and logical structure ?
Physical : Data files, Redo Log files, Control file.
Logical : Tables, Views, Tablespaces, etc.
Can you increase the size of a tablespace ? How ?
Yes, by adding datafiles to it.
What is the use of Control files ?
Contains pointers to locations of various data files, redo log files, etc.
What is the use of Data Dictionary ?
Used by Oracle to store information about
various physical and logical Oracle structures e.g. Tables,
Tablespaces, datafiles, etc
What are the advantages of clusters ?
Access time reduced for joins.
What are the disadvantages of clusters ?
The time for Insert increases.
Can Long/Long RAW be clustered ?
No.
Can null keys be entered in cluster index, normal index ?
Yes.
Can Check constraint be used for self referential integrity ? How ?
Yes. In the CHECK condition for a column
of a table, we can reference some other column of the same table and
thus enforce self referential integrity.
What are the min. extents allocated to a rollback extent ?
Two
What are the states of a rollback segment ? What is the difference between partly available and needs recovery ?
The various states of a rollback segment are :
ONLINE, OFFLINE, PARTLY AVAILABLE, NEEDS RECOVERY and INVALID.
What is the difference between unique key and primary key ?
Unique key can be null; Primary key cannot be null.
An insert statement followed by a create table statement followed by rollback ? Will the rows be inserted ?
No.
an you define multiple savepoints ?
Yes.
Can you Rollback to any savepoint ?
Yes.
What is the maximum no. of columns a table can have ?
254.
What is the significance of the & and && operators in PL SQL ?
The & operator means that the PL SQL
block requires user input for a variable. The && operator means
that the value of this variable should be the same as inputted by the
user previously for this same variable. If a transaction is very large,
and the rollback segment is not able to hold the rollback information,
then will the transaction span across different rollback segments or
will it terminate ? It will terminate (Please check ).
Can you pass a parameter to a cursor ?
Explicit cursors can take parameters, as
the example below shows. A cursor parameter can appear in a query
wherever a constant can appear. CURSOR c1 (median IN NUMBER) IS SELECT
job, ename FROM emp WHERE sal > median;
What are the various types of RollBack Segments ?
Public Available to all instances
Private Available to specific instance
Can you use %RowCount as a parameter to a cursor ?
Yes
Is the query below allowed :
Select sal, ename Into x From emp Where ename = 'KING'
(Where x is a record of Number(4) and Char(15))
Yes
Is the assignment given below allowed :
ABC = PQR (Where ABC and PQR are records)
Yes
Is this for loop allowed :
For x in &Start..&End Loop
Yes
How many rows will the following SQL return :
Select * from emp Where rownum < 10;
9 rows
How many rows will the following SQL return :
Select * from emp Where rownum = 10;
No rows
Which symbol preceeds the path to the table in the remote database ?
@
Are views automatically updated when base tables are updated ?
Yes
Can a trigger written for a view ?
No
If all the values from a
cursor have been fetched and another fetch is issued, the output will be
: error, last record or first record ?
Last Record
A table has the following data : [[5, Null, 10]]. What will the average function return ?
7.5
Is Sysdate a system variable or a system function?
System Function
Consider a sequence whose
currval is 1 and gets incremented by 1 by using the nextval reference we
get the next number 2. Suppose at this point we issue an rollback and
again issue a nextval. What will the output be ?
3
Definition of relational DataBase by Dr. Codd (IBM)?
A Relational Database is a database where
all data visible to the user is organized strictly as tables of data
values and where all database operations work on these tables.
What is Multi Threaded Server (MTA) ?
In a Single Threaded Architecture (or a
dedicated server configuration) the database manager creates a separate
process for each database user. But in MTA the database manager can
assign multiple users (multiple user processes) to a single dispatcher
(server process), a controlling process that queues request for work
thus reducing the databases memory requirement and resources.
Which are initial RDBMS, Hierarchical & N/w database ?
RDBMS - R system
Hierarchical - IMS
N/W - DBTG
What is Functional Dependency
Given a relation R, attribute Y of R is
functionally dependent on attribute X of R if and only if each X-value
has associated with it precisely one -Y value in R
What is Auditing ?
The database has the ability to audit all actions that take place within it.
a) Login attempts, b) Object Accesss, c) Database Action Result of Greatest(1,NULL) or Least(1,NULL) NULL
While designing in client/server what are the 2 imp. things to be considered ?
Network Overhead (traffic), Speed and Load of client server
When to create indexes ?
To be created when table is queried for less than 2% or 4% to 25% of the table rows.
How can you avoid indexes ?
TO make index access path unavailable -
Use FULL hint to optimizer for full table scan - Use INDEX or AND-EQUAL
hint to optimizer to use one index or set to indexes instead of another.
- Use an expression in the Where Clause of the SQL.
What is the result of the following SQL :
Select 1 from dual
UNION
Select 'A' from dual;
Error
Can database trigger written
on synonym of a table and if it can be then what would be the effect if
original table is accessed.
Yes, database trigger would fire.
Can you alter synonym of view or view ?
No
Can you create index on view ?
No
What is the difference between a view and a synonym ?
Synonym is just a second name of table
used for multiple link of database. View can be created with many
tables, and with virtual columns and with conditions. But synonym can be
on view.
What is the difference between alias and synonym ?
Alias is temporary and used with one query. Synonym is permanent and not used as alias.
What is the effect of synonym and table name used in same Select statement ?
Valid
What's the length of SQL integer ?
32 bit length
What is the difference between foreign key and reference key ?
Foreign key is the key i.e. attribute
which refers to another table primary key. Reference key is the primary
key of table referred by another table.
Can dual table be deleted, dropped or altered or updated or inserted ?
Yes
If content of dual is updated to some value computation takes place or not ?
Yes
If any other table same as dual is created would it act similar to dual?
Yes
For which relational operators in where clause, index is not used ?
<> , like '% ...' is NOT functions, field +constant, field || ''
Assume that there are multiple databases running on one machine. How can you switch from one to another ?
Changing the ORACLE_SID
What are the advantages of Oracle ?
Portability : Oracle is ported to more
platforms than any of its competitors, running on more than 100 hardware
platforms and 20 networking protocols.
Market Presence : Oracle is by far the largest RDBMS vendor and
spends more on R & D than most of its competitors earn in total
revenue. This market clout means that you are unlikely to be left in the
lurch by Oracle and there are always lots of third party interfaces
available.
Backup and Recovery : Oracle provides industrial strength support
for on-line backup and recovery and good software fault tolerence to
disk failure. You can also do point-in-time recovery.
Performance : Speed of a 'tuned' Oracle Database and application is
quite good, even with large databases. Oracle can manage > 100GB
databases.
Multiple database support : Oracle has a superior ability to manage
multiple databases within the same transaction using a two-phase commit
protocol.
What is a forward declaration ? What is its use ?
PL/SQL requires that you declare an
identifier before using it. Therefore, you must declare a subprogram
before calling it. This declaration at the start of a subprogram is
called forward declaration. A forward declaration consists of a
subprogram specification terminated by a semicolon.
What are actual and formal parameters ?
Actual Parameters : Subprograms pass
information using parameters. The variables or expressions referenced in
the parameter list of a subprogram call are actual parameters. For
example, the following procedure call lists two actual parameters named
emp_num and amount:
Eg. raise_salary(emp_num, amount);
Formal Parameters : The variables declared in a subprogram
specification and referenced in the subprogram body are formal
parameters. For example, the following procedure declares two formal
parameters named emp_id and increase: Eg. PROCEDURE raise_salary (emp_id
INTEGER, increase REAL) IS current_salary REAL;
What are the types of Notation ?
Position, Named, Mixed and Restrictions.
What all important parameters of the init.ora are supposed to be increased if you want to increase the SGA size ?
In our case, db_block_buffers was changed
from 60 to 1000 (std values are 60, 550 & 3500) shared_pool_size
was changed from 3.5MB to 9MB (std values are 3.5, 5 & 9MB)
open_cursors was changed from 200 to 300 (std values are 200 & 300)
db_block_size was changed from 2048 (2K) to 4096 (4K) {at the time of
database creation}.
The initial SGA was around 4MB when the server RAM was 32MB and The
new SGA was around 13MB when the server RAM was increased to 128MB.
If I have an execute
privilege on a procedure in another users schema, can I execute his
procedure even though I do not have privileges on the tables within the
procedure ?
Yes
What are various types of joins ?
Equijoins, Non-equijoins, self join, outer join
What is a package cursor ?
A package cursor is a cursor which you
declare in the package specification without an SQL statement. The SQL
statement for the cursor is attached dynamically at runtime from calling
procedures.
If you insert a row in a table, then create another table and then say Rollback. In this case will the row be inserted ?
Yes. Because Create table is a DDL
which commits automatically as soon as it is executed. The DDL commits
the transaction even if the create statement fails internally (eg table
already exists error) and not syntactically.
What are the various types of queries ??
Normal Queries
Sub Queries
Co-related queries
Nested queries
Compound queries
What is a transaction ?
A transaction is a set of SQL statements between any two COMMIT and ROLLBACK statements.
What is implicit cursor and how is it used by Oracle ?
An implicit cursor is a cursor which is internally created by Oracle. It is created by Oracle for each individual SQL.
Which of the following is not a schema object : Indexes, tables, public synonyms, triggers and packages ?
Public synonyms
What is PL/SQL?
PL/SQL is Oracle's Procedural Language
extension to SQL. The language includes object oriented programming
techniques such as encapsulation, function overloading, information
hiding (all but inheritance), and so, brings state-of-the-art
programming to the Oracle database server and a variety of Oracle tools.
Is there a PL/SQL Engine in SQL*Plus?
No. Unlike Oracle Forms, SQL*Plus does
not have a PL/SQL engine. Thus, all your PL/SQL are send directly to the
database engine for execution. This makes it much more efficient as SQL
statements are not stripped off and send to the database individually.
Is there a limit on the size of a PL/SQL block?
Currently, the maximum parsed/compiled
size of a PL/SQL block is 64K and the maximum code size is 100K. You can
run the following select statement to query the size of an existing
package or procedure.
SQL> select * from dba_object_size where name = 'procedure_name'
Can one read/write files from PL/SQL?
Included in Oracle 7.3 is a UTL_FILE
package that can read and write files. The directory you intend writing
to has to be in your INIT.ORA file (see UTL_FILE_DIR=... parameter).
Before Oracle 7.3 the only means of writing a file was to use
DBMS_OUTPUT with the SQL*Plus SPOOL command.
DECLARE
fileHandler UTL_FILE.FILE_TYPE;
BEGIN
fileHandler := UTL_FILE.FOPEN('/home/oracle/tmp', 'myoutput','W');
UTL_FILE.PUTF(fileHandler, 'Value of func1 is %sn', func1(1));
UTL_FILE.FCLOSE(fileHandler);
END;
How can I protect my PL/SQL source code?
PL/SQL V2.2, available with Oracle7.2,
implements a binary wrapper for PL/SQL programs to protect the source
code. This is done via a standalone utility that transforms the PL/SQL
source code into portable binary object code (somewhat larger than the
original). This way you can distribute software without having to worry
about exposing your proprietary algorithms and methods. SQL*Plus and
SQL*DBA will still understand and know how to execute such scripts. Just
be careful, there is no "decode" command available.
The syntax is:
wrap iname=myscript.sql oname=xxxx.yyy
Can one use dynamic SQL within PL/SQL? OR Can you use a DDL in a procedure ? How ?
From PL/SQL V2.1 one can use the DBMS_SQL package to execute dynamic SQL statements.
Eg: CREATE OR REPLACE PROCEDURE DYNSQL
AS
cur integer;
rc integer;
BEGIN
cur := DBMS_SQL.OPEN_CURSOR;
DBMS_SQL.PARSE(cur,'CREATE TABLE X (Y DATE)', DBMS_SQL.NATIVE);
rc := DBMS_SQL.EXECUTE(cur);
DBMS_SQL.CLOSE_CURSOR(cur);
END;
