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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










Configuring Retention Policy in RMAN

When you are taking backups regularly to a specified disk then after some period of time the backup disk will get full and you will need to delete old backups to make space for new backups.

Usually you delete the old backups manually by following a particular rule like, deleting all the backups taken before 1 month or keep 2 backup copies of datafiles and delete older copies.

Manually identifying and deleting old backup files is cumbersome. To help you out, Oracle RMAN has a feature called RETENTION POLICY.

By configuring Retention Policy in RMAN, you can easily delete old backups by just giving one command.

Let's see how to configure Retention Policy and how to delete old backups

Configuring Retention Policy

You can configure retention policy to either number of days or number of copies. By default the RETENTION POLICY is set to redundancy 1.

Configuring Retention Policy to number of copies

RMAN> configure retention policy to redundancy 2;

In the above command we are asking RMAN to keep 2 backup copies of each file. Backup copies which are older than 2 copies can be marked as obsolete and hence can be deleted.

configure retention policy to redundancy

Configuring Retention Policy to number of copies

RMAN> configure retention policy to recovery window of 15 days;

When we issue this command RMAN will mark obsolete those backups which are older than 15 days.

configure retention policy to days

Viewing obsolete backups

To view backups which have become obsolete according to the current retention policy you can give the following command

RMAN> report obsolete;

report obsolete in oracle rman

Deleting Obsolete Backups

We can delete obsolete backups by giving the following command

RMAN> delete obsolete;

delete obsolete backupsets

Once retention policy is configured we can anytime issue the above command to delete old backups and free up space.

Checking the status of Retention Policy

Type the following command to know the currently configured RETENTION POLICY

RMAN> show retention policy;

show retention policy

Resetting RETENTION POLICY to default

You can reset the RETENTION POLICY to default value by giving the following command

RMAN> configure retention policy clear;

reset retention policy


You can also disable retention policy. Disabling makes RMAN not consider any backup as obsolete

disable retention policy



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