Oracle Database Questions & Answers 3

61. What constitute an ORACLE Instance ?
SGA and ORACLE background processes constitute an ORACLE instance. (or) Combination of memory

structure and background process.

62. What is SGA ?
The System Global Area (SGA) is a shared memory region allocated by ORACLE that contains data and

control information for one ORACLE instance.

63. What are the components of SGA ?
Database buffers, Redo Log Buffer the Shared Pool and Cursors.

64. What do Database Buffers contain ?
Database buffers store the most recently used blocks of database data. It can also contain modified

data that has not yet been permanently written to disk.

65. What do Redo Log Buffers contain ?
Redo Log Buffer stores redo entries a log of changes made to the database.

66. What is Shared Pool ?
Shared Pool is a portion of the SGA that contains shared memory constructs such as shared SQL areas.

67. What is Shared SQL Area ?
A Shared SQL area is required to process every unique SQL statement submitted to a database and

contains information such as the parse tree and execution plan for the corresponding statement.

68. What is Cursor ?
A Cursor is a handle ( a name or pointer) for the memory associated with a specific statement.

69. What is PGA ?
Program Global Area (PGA) is a memory buffer that contains data and control information for a server


70. What is User Process ?
A user process is created and maintained to execute the software code of an application program. It

is a shadow process created automatically to facilitate communication between the user and the

server process.

71. What is Server Process ?
Server Process handle requests from connected user process. A server process is in charge of

communicating with the user process and interacting with ORACLE carry out requests of the associated

user process.

72. What are the two types of Server Configurations ?
Dedicated Server Configuration and Multi-threaded Server Configuration.

73. What is Dedicated Server Configuration ?
In a Dedicated Server Configuration a Server Process handles requests for a Single User Process.

74. What is a Multi-threaded Server Configuration ?
In a Multi-threaded Server Configuration many user processes share a group of server process.

75. What is a Parallel Server option in ORACLE ?
A configuration for loosely coupled systems where multiple instance share a single physical database

is called Parallel Server.

76. Name the ORACLE Background Process ?
DBWR – Database Writer.
LGWR – Log Writer
CKPT – Check Point
SMON – System Monitor
PMON – Process Monitor
ARCH – Archiver
RECO – Recover
Dnnn – Dispatcher, and
LCKn – Lock
Snnn – Server.

77. What Does DBWR do ?
Database writer writes modified blocks from the database buffer cache to the data files.

78.When Does DBWR write to the database ?
DBWR writes when more data needs to be read into the SGA and too few database buffers are free. The

least recently used data is written to the data files first. DBWR also writes when CheckPoint


79. What does LGWR do ?
Log Writer (LGWR) writes redo log entries generated in the redo log buffer of the SGA to on-line

Redo Log File.

80. When does LGWR write to the database?
LGWR writes redo log entries into an on-line redo log file when transactions commit and the log

buffer files are full.

81. What is the function of checkpoint CKPT)?
The Checkpoint (CKPT) process is responsible for signaling DBWR at checkpoints and updating all the

data files and control files of the database.

82. What are the functions of SMON ?
System Monitor (SMON) performs instance recovery at instance start-up. In a multiple instance system

(one that uses the Parallel Server), SMON of one instance can also perform instance recovery for

other instance that have failed SMON also cleans up temporary segments that are no longer in use and

recovers dead transactions skipped during crash and instance recovery because of file-read or

off-line errors. These transactions are eventually recovered by SMON when the tablespace or file is

brought back on-line SMON also coalesces free extents within the database to make free space

contiguous and easier to allocate.

83. What are functions of PMON ?
Process Monitor (PMON) performs process recovery when a user process fails PMON is responsible for

cleaning up the cache and Freeing resources that the process was using PMON also checks on

dispatcher and server processes and restarts them if they have failed.

84. What is the function of ARCH ?
Archiver (ARCH) copies the on-line redo log files to archival storage when they are full. ARCH is

active only when a database’s redo log is used in ARCHIVELOG mode.

85. What is function of RECO ?
RECOver (RECO) is used to resolve distributed transactions that are pending due to a network or

system failure in a distributed database. At timed intervals,the local RECO attempts to connect to

remote databases and automatically complete the commit or rollback of the local portion of any

pending distributed transactions.

86. What is the function of Dispatcher (Dnnn) ?
Dispatcher (Dnnn) process is responsible for routing requests from connected user processes to

available shared server processes and returning the responses back to the appropriate user


87. How many Dispatcher Processes are created ?
Atleast one Dispatcher process is created for every communication protocol in use.

88. What is the function of Lock (LCKn) Process ?
Lock (LCKn) are used for inter-instance locking when the ORACLE Parallel Server option is used.

89. What is the maximum number of Lock Processes used ?
Though a single LCK process is sufficient for most Parallel Server systems
upto Ten Locks (LCK0,….LCK9) are used for inter-instance locking.


90. Define Transaction ?
A Transaction is a logical unit of work that comprises one or more SQL statements executed by a

single user.

91. When does a Transaction end ?
When it is committed or Rollbacked.

92. 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.

93. What does ROLLBACK do ?
ROLLBACK retracts any of the changes resulting from the SQL statements in the transaction.

94. 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.

95. 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.

96. What is the function of Optimizer ?
The goal of the optimizer is to choose the most efficient way to execute a SQL statement.

97. What is Execution Plan ?
The combinations of the steps the optimizer chooses to execute a statement is called an execution


98. What are the different approaches used by Optimizer in choosing an execution plan ?
Rule-based and Cost-based.

99. What are the factors that affect OPTIMIZER in choosing an Optimization approach ?
The OPTIMIZER_MODE initialization parameter Statistics in the Data Dictionary the OPTIMIZER_GOAL

parameter of the ALTER SESSION command hints in the statement.

100. What are the values that can be specified for OPTIMIZER MODE Parameter ?

101. Will the Optimizer always use COST-based approach if OPTIMIZER_MODE is set to “Cost’?
Presence of statistics in the data dictionary for atleast one of the tables accessed by the SQL

statements is necessary for the OPTIMIZER to use COST-based approach. Otherwise OPTIMIZER chooses

RULE-based approach.

102. What is the effect of setting the value of OPTIMIZER_MODE to ‘RULE’ ?
This value causes the optimizer to choose the rule_based approach for all SQL statements issued to

the instance regardless of the presence of statistics.

103. What are the values that can be specified for OPTIMIZER_GOAL parameter of the ALTER SESSION

Command ?

104. 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.

105. What is the effect of setting the value “ALL_ROWS” for OPTIMIZER_GOAL parameter of the ALTER

SESSION command ?
This value causes the optimizer to the cost-based approach for all SQL statements in the session

regardless of the presence of statistics and to optimize with a goal of best throughput.

106. What is the effect of setting the value ‘FIRST_ROWS’ for OPTIMIZER_GOAL parameter of the ALTER

SESSION command ?
This value causes the optimizer to use the cost-based approach for all SQL statements in the session

regardless of the presence of statistics and to optimize with a goal of best response time.

107. What is the effect of setting the ‘RULE’ for OPTIMIER_GOAL parameter of the ALTER SESSION

Command ?
This value causes the optimizer to choose the rule-based approach for all SQL statements in a

session regardless of the presence of statistics.

108. What is RULE-based approach to optimization ?
Choosing an executing planbased on the access paths available and the ranks of these access paths.

109. 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.


110. 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.

111. 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.

112. What is difference between Procedures and Functions ?
A Function returns a value to the caller where as a Procedure does not.

113. 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.

114. 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)

115. 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.

116. 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.

117. What are the differences between Database Trigger and Integrity constraints ?
A declarative integrity constraint is a statement about the database that is always true. A

constraint applies to existing data in the table and any statement that manipulates the table.
A trigger does not apply to data loaded before the definition of the trigger, therefore, it does not

guarantee all data in a table conforms to the rules established by an associated trigger.
A trigger can be used to enforce transitional constraints where as a declarative integrity

constraint cannot be used.


118. What are Roles ?
Roles are named groups of related privileges that are granted to users or other roles.

119. 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.

120. How to prevent unauthorized use of privileges granted to a Role ?
By creating a Role with a password.

121. What is default tablespace ?
The Tablespace to contain schema objects created without specifying a tablespace name.

122. What is Tablespace Quota ?
The collective amount of disk space available to the objects in a schema on a particular tablespace.

123. What is a profile ?
Each database user is assigned a Profile that specifies limitations on various system resources

available to the user.

124. 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.

125. What is Auditing ?
Monitoring of user access to aid in the investigation of database use.

126. What are the different Levels of Auditing ?
Statement Auditing, Privilege Auditing and Object Auditing.

127. What is Statement Auditing ?
Statement auditing is the auditing of the powerful system privileges without regard to specifically

named objects.

128. What is Privilege Auditing ?
Privilege auditing is the auditing of the use of powerful system privileges without regard to

specifically named objects.

129. What is Object Auditing ?
Object auditing is the auditing of accesses to specific schema objects without regard to user.


130. 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.

131. 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.

132. 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.

133. What is the mechanism provided by ORACLE for table replication ?
Snapshots and SNAPSHOT LOGs

134. 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.

135. 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.

136. 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.


137. What are the steps involved in Database Startup ?
Start an instance, Mount the Database and Open the Database.

138. What are the steps involved in Database Shutdown ?
Close the Database, Dismount the Database and Shutdown the Instance.

139. 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.

140. 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.

141. 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.

142. Can Full Backup be performed when the database is open ?

143. 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.

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.

145. 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.

146. What is Archived Redo Log ?
Archived Redo Log consists of Redo Log files that have archived before being reused.

147. What are the advantages of operating a database in ARCHIVELOG mode over operating it in NO

Complete database recovery from disk failure is possible only in ARCHIVELOG mode.
Online database backup is possible only in ARCHIVELOG mode.

148. 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.

149. What are the steps involved in Instance Recovery ?
R_olling 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.

1. 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.

2. What is Parallel Server ?
Multiple instances accessing the same database (Only In Multi-CPU environments)

3. What is a Schema ?
The set of objects owned by user account is called the schema.

4. 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)

5. What is clusters ?
Group of tables physically stored together because they share common columns and are often used

together is called Cluster.

6. 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.

7. 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)
CKPT (Check Point)
User Process with associated PGS

8. 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.


9. What is SGA ? How it is different from Ver 6.0 and Ver 7.0 ?
The System Global Area in a Oracle database is the area in memory to facilitates 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 SQL pool (ver 7.0

only) area.

10. 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.

11. What is mean by Program Global Area (PGA) ?
It is area in memory that is used by a Single Oracle User Process.

12. 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.

13. 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.


14. 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.

15. What is dictionary cache ?
Dictionary cache is information about the databse objects stored in a data dictionary table.

16. 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.

17. What is meant by redo log buffer ?
Change 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.

18. 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.

19. List the Optional Flexible Architecture (OFA) of Oracle database ? or How can we organise 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.

20. How will you force database to use particular rollback segment ?

21. 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.

22. 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

23.Which parameter in Storage clause will reduce no. of rows per block?
PCTFREE parameter
Row size also reduces no of rows per block.

24. 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.,

25. How does Space allocation table place within a block ?
Each block contains entries as follows
Fixied block header
Variable block header
Row Header,row date (multiple rows may exists)
PCTEREE (% of free space for row updation in future)

26. What is the role of PCTFREE parameter is Storage clause ?
This is used to reserve certain amount of space in a block for expansion of rows.

27. What is the OPTIMAL parameter ?
It is used to set the optimal length of a rollback segment.

28. What is the functionality of SYSTEM table space ?
To manage the database level transactions such as modifications of the data dictionary table that

record information about the free space usage.

29. 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.

30. How the space utilisation takes place within rollback segments ?
It will try to fit the transaction in a cyclic fashion to all existing extents. Once it found an

extent is in use then it forced to acquire a new extent (No. of extents is based on the optimal


31. Why query fails sometimes ?
Rollback segment dynamically extent to handle larger transactions entry loads.
A single transaction may wipeout all avaliable free space in the Rollback Segment Tablespace. This

prevents other user using Rollback segments.

32. How will you monitor the space allocation ?
By quering DBA_SEGMENT table/view.

33. 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.

34. List the sequence of events when a large transaction that exceeds beyond its optimal value when

an entry wraps and causes the rollback segment to expand into another extend.
Transaction Begins.
An entry is made in the RES header for new transactions entry
Transaction acquires blocks in an extent of RBS
The entry attempts to wrap into second extent. None is available, so that the RBS must extent.
The RBS checks to see if it is part of its OPTIMAL size.
RBS chooses its oldest inactive segment.
Oldest inactive segment is eliminated.
RBS extents
The Data dictionary table for space management are updated.
Transaction Completes.

35. How can we plan storage for very large tables ?
Limit the number of extents in the table
Separate Table from its indexes.
Allocate Sufficient temporary storage.

36. 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.

37. It is possible to use raw devices as data files and what is the advantages over file. system

files ?
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.

38. What is a Control file ?
Database’s 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.

39. How to implement the multiple control files for an existing database ?
Shutdown the databse
Copy one of the existing control file to new location
Edit Config ora file by adding new control
Restart the database.

40. What is meant by Redo Log file mirrorring ? 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.

41. 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


42. What is use of Rollback Segments In Database ?
They allow the database to maintain read consistency between multiple transactions.

43. 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.

44. 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.

45. When will be a segment released ?
When Segment is dropped.
When Shrink (RBS only)
When truncated (TRUNCATE used with drop storage option)

46. What are disadvanteges 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.

47. List the factors that can affect the accuracy of the estimations ?
The space used transaction entries and deleted records does not become free immediately after

completion due to delayed cleanout.
Trailling nulls and length bytes are not stored.
Inserts of, updates to and deletes of rows as well as columns larger than a single datablock, can

cause fragmentation an chained row pieces.


48. 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.

49. 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.

50. What are the dictionary tables used to monitor a database spaces ?

Data Base Administration

51. 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 Oracle license agreement
Controlling and monitoring user access to the database.
Monitoring and optimising 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.

52. 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 basetables 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.

54. 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

Export (EXP) and Import (imp) utilities allow you to move existing data in ORACLE format to and from

ORACLE database.

55. 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.

56. 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.

57. 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 provies to roles.
Assign each role to group of users. This will simplify the job of assigning privileges to individual


58. What are the steps to switch a database’s archiving mode between NO ARCHIVELOG and ARCHIVELOG

mode ?
1. Shutdown the database instance.
2. Backup the database
3. Perform any operating system specific steps (optional)
4. Start up a new instance and mount but do not open the database.
5. Switch the database’s archiving mode.

59. 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.

60. 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.

61. 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.


62. How can we reduce the network traffic ?
– Replication of data in distributed environment.
– Using snapshots to replicate data.
– Using remote procedure calls.

63. 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.

64. What are the various type of snapshots ?
Simple and Complex.

65. 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 snapshot of operations.
– A complex snapshots contain at least any one of the above.

66. What dynamic data replication ?
Updating or Inserting records in remote database through database triggers. It may fail if remote

database is having any problem.

67. How can you Enforce Referential Integrity in snapshots ?
Time the references to occur when master tables are not in use.
Perform the reference the manually immediately locking the master tables. We can join tables in

snapshots by creating a complex snapshots that will based on the master tables.

68. What are the options available to refresh snapshots ?
COMPLETE – Tables are completely regenerated using the snapshot’s 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

FORCE – Default value. If possible it performs a FAST refresh; Otherwise it will perform a complete


69. 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.

70. 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).

72. 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.


73. What are the different methods of backing up oracle database ?
– Logical Backups
– Cold Backups
– Hot Backups (Archive log)

74. 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.

75. 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

– All Data files.
– All Control files.
– All on-line redo log files.
– The init.ora file (Optional)

76. 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.

77. 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.

78. What is the use of FILE option in EXP command ?
To give the export file name.

79. What is the use of COMPRESS option in EXP command ?
Flag to indicate whether export should compress fragmented segments into single extents.

80. What is the use of GRANT option in EXP command ?
A flag to indicate whether grants on database objects will be exported or not. Value is ‘Y’ or ‘N’.

81. What is the use of INDEXES option in EXP command ?
A flag to indicate whether indexes on tables will be exported.

82. 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.

83. What is the use of CONSTRAINTS option in EXP command ?
A flag to indicate whether constraints on table need to be exported.

84. What is the use of FULL option in EXP command ?
A flag to indicate whether full database export should be performed.

85. What is the use of OWNER option in EXP command ?
List of table accounts should be exported.

86. What is the use of TABLES option in EXP command ?
List of tables should be exported.

87. What is the use of RECORD LENGTH option in EXP command ?
Record length in bytes.

88. What is the use of INCTYPE option in EXP command ?
Type export should be performed COMPLETE,CUMULATIVE,INCREMENTAL.

89. 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.

90. What is the use of PARFILE option in EXP command ?
Name of the parameter file to be passed for export.

91. What is the use of PARFILE option in EXP command ?
Name of the parameter file to be passed for export.

92. 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.

93. 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


94. What is use of LOG (Ver 7) option in EXP command ?
The name of the file which log of the export will be written.

95.What is the use of FILE option in IMP command ?
The name of the file from which import should be performed.

96. What is the use of SHOW option in IMP command ?
A flag to indicate whether file content should be displayed or not.

97. 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.

98. What is the use of GRANT option in IMP command ?
A flag to indicate whether grants on database objects will be imported.

99. What is the use of INDEXES option in IMP command ?
A flag to indicate whether import should import index on tables or not.

100. 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.

1. SNAPSHOT is used for
[DBA] a] Synonym, b] Table space, c] System server, d] Dynamic data
Ans : D

2. We can create SNAPSHOTLOG for
[DBA] a] Simple snapshots, b] Complex snapshots, c] Both A & B, d]
Neither A nor B
Ans : A

3. Transactions per rollback segment is derived from
[DBA] a] Db_Block_Buffers, b] Processes, c] Shared_Pool_Size, d] None
of the above
Ans : B

4. ENQUEUE resources parameter information is derived from
[DBA] a] Processes or DDL_LOCKS and DML_LOCKS, b] LOG_BUFFER,
Ans : A

5. LGWR process writes information into
a] Database files, b] Control files, c] Redolog files, d] All the
Ans : C

in a particular Tablespace
a] True, b] False
Ans : False

7. Databases overall structure is maintained in a file called
a] Redolog file, b] Data file, c] Control file, d] All of the
Ans : C

8. These following parameters are optional in init.ora parameter file
a] True, b] False
Ans : False

9. Constraints cannot be exported through EXPORT command
a] True, b] False
Ans : False

10. It is very difficult to grant and manage common privileges needed by
different groups of
database users using the roles
a] True, b] False
Ans : False

11. What is difference between a DIALOG WINDOW and a DOCUMENT WINDOW
moving the window with respect to the application window
a] Both windows behave the same way as far as moving the window is
b] A document window can be moved outside the application window while
a dialog
window cannot be moved
c] A dialog window can be moved outside the application window while a
window cannot be moved
Ans : C

12. What is the difference between a MESSAGEBOX and an ALERT
a] A messagebox can be used only by the system and cannot be used in
user application
while an alert can be used in user application also.
b] A alert can be used only by the system and cannot be use din user
while an messagebox can be used in user application also.
c] An alert requires an response from the userwhile a messagebox just
flashes a message
and only requires an acknowledment from the user
d] An message box requires an response from the userwhile a alert just
flashes a
message an only requires an acknowledment from the user
Ans : C

13. Which of the following is not an reason for the fact that most of the
processing is done at the
server ?
a] To reduce network traffic. b] For application sharing, c] To
implement business rules
centrally, d] None of the above
Ans : D

14. Can a DIALOG WINDOW have scroll bar attached to it ?
a] Yes, b] No
Ans : B

15. Which of the following is not an advantage of GUI systems ?
a] Intuitive and easy to use., b] GUI’s can display multiple
applications in multiple windows
c] GUI’s provide more user interface objects for a developer
d] None of the above
Ans 😀

16. What is the difference between a LIST BOX and a COMBO BOX ?
a] In the list box, the user is restricted to selecting a value from a
list but in a combo box
the user can type in a value which is not in the list
b] A list box is a data entry area while a combo box can be used only
for control purposes
c] In a combo box, the user is restricted to selecting a value from a
list but in a list box the
user can type in a value which is not in the list
d] None of the above
Ans : A

17. In a CLIENT/SERVER environment , which of the following would not be
done at the client ?
a] User interface part, b] Data validation at entry line, c]
Responding to user events,
d] None of the above
Ans : D

18. Why is it better to use an INTEGRITY CONSTRAINT to validate data in a
table than to use a
a] Because an integrity constraint is automatically checked while data
is inserted into or
updated in a table while a stored procedure has to be
specifically invoked
b] Because the stored procedure occupies more space in the database
than a integrity
constraint definition
c] Because a stored procedure creates more network traffic than a
integrity constraint
Ans : A

19. Which of the following is not an advantage of a client/server model ?
a] A client/server model allows centralised control of data and
centralised implementation
of business rules.
b] A client/server model increases developer;s productivity
c] A client/server model is suitable for all applications
d] None of the above.
Ans : C

20. What does DLL stands for ?
a] Dynamic Language Library
b] Dynamic Link Library
c] Dynamic Load Library
d] None of the above
Ans : B

21. POST-BLOCK trigger is a
a] Navigational trigger
b] Key trigger
c] Transactional trigger
d] None of the above
Ans : A

22. The system variable that records the select statement that SQL * FORMS
most recently used
to populate a block is
Ans: D

23. Which of the following is TRUE for the ENFORCE KEY field
a] ENFORCE KEY field characterstic indicates the source of the value
uses to populate the field
b] A field with the ENFORCE KEY characterstic should have the INPUT
charaterstic turned off
a] Only 1 is TRUE
b] Only 2 is TRUE
c] Both 1 and 2 are TRUE
d] Both 1 and 2 are FALSE
Ans : A

24. What is the maximum size of the page ?
a] Characters wide & 265 characters length
b] Characters wide & 265 characters length
c] Characters wide & 80 characters length
d] None of the above
Ans : B

25. A FORM is madeup of which of the following objects
a] block, fields only,
b] blocks, fields, pages only,
c] blocks, fields, pages, triggers and form level procedures,
d] Only blocks.
Ans : C

26. For the following statements which is true
1] Page is an object owned by a form
2] Pages are a collection of display information such as constant text
and graphics.
a] Only 1 is TRUE
b] Only 2 is TRUE
c] Both 1 & 2 are TRUE
d] Both are FALSE
Ans : B

27. The packaged procedure that makes data in form permanent in the
Database is
a] Post
b] Post form
c] Commit form
d] None of the above
Ans : C

28. Which of the following is TRUE for the SYSTEM VARIABLE $$date$$
a] Can be assigned to a global variable
b] Can be assigned to any field only during design time
c] Can be assigned to any variable or field during run time
d] None of the above
Ans : B

29. Which of the following packaged procedure is UNRESTRICTED ?
Ans : D

30. Identify the RESTRICTED packaged procedure from the following
Ans : D

31. What is SQL*FORMS
a] SQL*FORMS is a 4GL tool for developing & executing Oracle based
b] SQL*FORMS is a 3GL tool for connecting to the Database.
c] SQL*FORMS is a reporting tool
d] None of the above.
Ans : A

32. Name the two files that are created when you generate a form using
Forms 3.0
a] FMB & FMX, b] FMR & FDX, c] INP & FRM, d] None of the above
Ans : C

33. What is a trigger
a] A piece of logic written in PL/SQL
b] Executed at the arrival of a SQL*FORMS event
c] Both A & B
d] None of the above
Ans : C

34. Which of the folowing is TRUE for a ERASE packaged procedure
1] ERASE removes an indicated Global variable & releases the memory
associated with it
2] ERASE is used to remove a field from a page
1] Only 1 is TRUE
2] Only 2 is TRUE
3] Both 1 & 2 are TRUE
4] Both 1 & 2 are FALSE
Ans : 1

35. All datafiles related to a Tablespace are removed when the Tablespace
is dropped
Ans : B

36. Size of Tablespace can be increased by
a] Increasing the size of one of the Datafiles
b] Adding one or more Datafiles
c] Cannot be increased
d] None of the above
Ans : B

37. Multiple Tablespaces can share a single datafile
Ans : B

38. A set of Dictionary tables are created
a] Once for the Entire Database
b] Every time a user is created
c] Every time a Tablespace is created
d] None of the above
Ans : A

39. Datadictionary can span across multiple Tablespaces
Ans : B

40. What is a DATABLOCK
a] Set of Extents
b] Set of Segments
c] Smallest Database storage unit
d] None of the above
Ans : C

41. Can an Integrity Constraint be enforced on a table if some existing
table data does not satisfy
the constraint
a] Yes
b] No
Ans : B

42. A column defined as PRIMARY KEY can have NULL’s
Ans : B

43. A Transaction ends
a] Only when it is Committed
b] Only when it is Rolledback
c] When it is Committed or Rolledback
d] None of the above
Ans : C

44. A Database Procedure is stored in the Database
a] In compiled form
b] As source code
c] Both A & B
d] Not stored
Ans : C

45. A database trigger doesnot apply to data loaded before the definition
of the trigger
Ans : A

46. Dedicated server configuration is
a] One server process – Many user processes
b] Many server processes – One user process
c] One server process – One user process
d] Many server processes – Many user processes
Ans : C

47. Which of the following does not affect the size of the SGA
a] Database buffer
b] Redolog buffer
c] Stored procedure
d] Shared pool
Ans : C

48. What does a COMMIT statement do to a CURSOR
a] Open the Cursor
b] Fetch the Cursor
c] Close the Cursor
d] None of the above
Ans : D

49. Which of the following is TRUE
1] Host variables are declared anywhere in the program
2] Host variables are declared in the DECLARE section
a] Only 1 is TRUE
b] Only 2 is TRUE
c] Both 1 & 2are TRUE
d] Both are FALSE
Ans : B

50. Which of the following is NOT VALID is PL/SQL
a] Bool boolean;
b] NUM1, NUM2 number;
c] deptname dept.dname%type;
d] date1 date := sysdate
Ans : B.