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Oracle DBA Interview Questions

Most asked Oracle DBA Interview Questions.

60 Technical Questions
42 Backup & Recovery Questions

Unix For Oracle DBA 20 Questions

Oracle DBA Topics

Overview of Oracle Grid Architecture

Difference between cluster and grid

Responsibilities of DBA's

Creating Oracle Database

Creating Database using SQL

Creating DB in 12c using DBCA

Creating DB in 12c using SQL commands

Managing Oracle 12c Container Databases

Creating Users in Oracle 12c

Managing Pluggable Databases in Oracle 12c

Creating Pluggable Database

Cloning Pluggable Database

Unplug and Plug databases in CDB's

Managing Tablespaces and Datafiles

Extending tablespaces

Decreasing size of a tablespace

Coalescing Tablespaces

Taking tablespaces Offline or Online

Making a Tablespace Read only

Renaming Tablespaces

Dropping Tablespaces

Viewing Info about Tablespaces

Renaming Datafiles

Relocating Datafiles

Relocating Datafiles in Multiple Tablespaces

Temporary Tablespace

Changing the size

Tablespace Groups

Creating a Temp. Tablespace Group

Assigning a Tablespace Group

Diagnosing and Repairing LMT

Scenario 1: Fixing Bitmap

Scenario 2: Dropping a Corrupted Segment

Scenario 3: Fixing Bitmap when Overlapped

Scenario 4: Correcting Corruption of Blocks

Scenario 5: Migrating from a Dictionary-Managed to LMT

Transporting Tablespaces

Procedure for transporting tablespaces

Transporting Tablespace Example


Adding New Redo Logfile Group

Adding Members to group

Dropping Members from group

Dropping Logfile Group

Resizing Logfiles

Renaming or Relocating Logfiles


Viewing Info About Logfiles

Managing Control Files

Multiplexing Control File

Changing the Name of a Database

Creating A New Control File

Cloning an Oracle Database


Switching to Automatic Management

Calculate Undo Retention

Altering UNDO Tablespace

Dropping an Undo Tablespace

Switching Undo Tablespaces

Viewing Information

SQL Loader


From Fixed Length file

From MySQL to Oracle

Using WHEN condition

Conventional and Direct Path Load

Direct Path

Restrictions on Using Direct Path Loads

Export and Import

Invoking Export and Import

Parameters of Export tool

Exporting Full Database

Exporting Schemas

Exporting Tables

Exporting Consistent Image of tables

Using Import Utility

Example Importing Tables

Import from One User to another User

Using Pattern Matching

Migrating a Database across platforms


Data Pump Export

Exporting a Full Database

Exporting a Schema

Exporting Individual Tables

Filtering Objects during Export

Filter Rows during Export

Suspending and Resuming Export

Data Pump Import Utility

Importing Full Dump File

Importing Objects between Schemas

Loading Objects between Tablespaces

Generating SQL File of DDL commands

Import objects of a Schema

Importing Only Particular Tables

Interactive Mode

Flash Back Features

Flashback Query

Flashback Version Query

Flashback Table to Past States

Purging Objects from Recycle Bin

Flashback Objects With Same Name

Flashback instead of PIT Recovery

Enabling Flash Back Database

Sizing flash recovery area

How far we can flashback database

Example:Flashing Back Database

Flashback Data Archive (FDA)
(Oracle Total Recall)


Creating FDA tablespace

Creating FDA

Querying historical data

Log Miner

LogMiner Configuration

LogMiner Dictionary Options

Using the Online Catalog

Extracting Dictionary to Log Files

Extracting Dictionary to File

Redo Log File Options

Example: Finding All Modifications

Mining Logfiles in a Time Range


Opening DB in Archivelog Mode

Reverting back to NoArchiveLog mode

Taking Offline (COLD) Backups

Taking Online (HOT) Backups

Recovering from the Loss of a Datafile

When in Noarchivelog Mode

When in Archivelog Mode

Recovering from loss of Control File

Recovery Manager ( RMAN )

Offline Backups using RMAN

Recover DB when in NOARCHIVELOG

Online Backups using RMAN

Backup tablespaces or datafiles

Image Backups in RMAN

Incremental Backup using RMAN

Updating backup copy for fast recovery

View info about RMAN backups

Configuring Retention policy

Configure Options in RMAN

Maintaining RMAN Repository

Recover datafiles (Archivelog mode)

Recover datafiles by renaming

Performing Disaster Recovery










View information and rename tablespaces and datafiles

Viewing Information about Tablespaces and Datafiles

Oracle has provided many Data dictionaries to view information about tablespaces and datafiles.  Some of them are:

To view information about Tablespaces in a database give the following query

SQL> select * from dba_tablespaces
SQL> select * from v$tablespace;

To view information about Datafiles

SQL> select * from dba_data_files;
SQL> select * from v$datafile;

To view information about Tempfiles

SQL> select * from dba_temp_files;
SQL> select * from v$tempfile;

To view information about free space in datafiles

SQL> select * from dba_free_space;

To view information about free space in tempfiles

SQL> select * from V$TEMP_SPACE_HEADER;

Renaming or Relocating Datafiles belonging to a Single Tablespace

You can rename datafiles to either change their names or relocate them.

To rename or relocate datafiles belonging to a Single Tablespace do the following.

1.       Take the tablespace offline

2.       Rename or Relocate the datafiles using operating system command

3.       Give the ALTER TABLESPACE with RENAME DATAFILE option to change the filenames within the Database.

4.       Bring the tablespace Online

For Example suppose you have a tablespace users with the following datafiles


Now you want to relocate /u01/oracle/ica/usr01.dbf’  to ‘/u02/oracle/ica/usr01.dbf’ and want to rename ‘/u01/oracle/ica/usr02.dbf’ to ‘/u01/oracle/ica/users02.dbf’  then follow the given the steps

1.       Bring the tablespace offline

SQL> alter tablespace users offline;

2.       Copy the file to new location using o/s command.

$ cp /u01/oracle/ica/usr01.dbf  /u02/oracle/ica/usr01.dbf’

Rename the file ‘/u01/oracle/ica/usr02.dbf’ to ‘/u01/oracle/ica/users02.dbf’ using o/s command.

$ mv  /u01/oracle/ica/usr02.dbf /u01/oracle/ica/users02.dbf

3.       Now start SQLPLUS and type the following command to rename and relocate these files

 SQL> alter tablespace users rename file  ‘/u01/oracle/ica/usr01.dbf’, 
        ‘/u01/oracle/ica/usr02.dbf’ to ‘/u02/oracle/ica/usr01.dbf’, ’/u01/oracle/ica/users02.dbf’;

4.       Now bring the tablespace  Online

SQL> alter tablespace users online;

Procedure for Renaming and Relocating Datafiles in Multiple Tablespaces

You can rename and relocate datafiles in one or more tablespaces using the ALTER DATABASE RENAME FILE statement. This method is the only choice if you want to rename or relocate datafiles of several tablespaces in one operation. You must have the ALTER DATABASE system privilege

To rename datafiles in multiple tablespaces, follow these steps.

1.      Ensure that the database is mounted but closed.

2.      Copy the datafiles to be renamed to their new locations and new names, using the operating system..

3.      Use ALTER DATABASE to rename the file pointers in the database control file.

For example, the following statement renames the datafiles/u02/oracle/rbdb1/sort01.dbf and /u02/oracle/rbdb1/user3.dbf to /u02/oracle/rbdb1/temp01.dbf and /u02/oracle/rbdb1/users03.dbf, respectively:

    RENAME FILE '/u02/oracle/rbdb1/sort01.dbf',
             TO '/u02/oracle/rbdb1/temp01.dbf',

Always provide complete filenames (including their paths) to properly identify the old and new datafiles. In particular, specify the old datafile names exactly as they appear in the DBA_DATA_FILES view.

4.      Back up the database. After making any structural changes to a database, always perform an immediate and complete backup.

5.      Start the Database




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