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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










Data Pump Import Utility Examples  

Objects exported by Data Pump Export Utility can be imported into a database using Data Pump Import Utility. The following describes how to use Data Pump Import utility to import objects

Importing Full Dump File

If you want to Import all the objects in a dump file you can type the following command.

$impdp hr/hr DUMPFILE=dpump_dir1:expfull.dmp FULL=y

This example imports everything from the expfull.dmp dump file. In this example, a DIRECTORY parameter is not provided. Therefore, a directory object must be provided on both the DUMPFILE parameter and the LOGFILE parameter

Importing Objects of One Schema to another Schema

The following example loads all tables belonging to hr schema to scott schema

$ impdp SYSTEM/password DIRECTORY=dpump_dir1 DUMPFILE=hr.dmp

If SCOTT account exist in the database then hr objects will be loaded into scott schema. If scott account does not exist, then Import Utility will create the SCOTT account with an unusable password because, the dump file was exported by the user SYSTEM and imported by the user SYSTEM who has DBA privileges.

Loading Objects of one Tablespace to another Tablespace.

You can use remap_tablespace option to import objects of one tablespace to another tablespace by giving the command

$ impdp SYSTEM/password DIRECTORY=dpump_dir1 DUMPFILE=hr.dmp

The above example loads tables, stored in users tablespace, in the sales tablespace.

Generating SQL File containing DDL commands using Data Pump Import

You can generate SQL file which contains all the DDL commands which Import would have executed if you actually run Import utility

The following is an example of using the SQLFILE parameter.

$ impdp hr/hr DIRECTORY=dpump_dir1 DUMPFILE=expfull.dmp

A SQL file named expfull.sql is written to dpump_dir2.

Importing objects of only a Particular Schema

If you have the IMP_FULL_DATABASE role, you can use this parameter to perform a schema-mode import by specifying a single schema other than your own or a list of schemas to import. First, the schemas themselves are created (if they do not already exist), including system and role grants, password history, and so on. Then all objects contained within the schemas are imported. Nonprivileged users can specify only their own schemas. In that case, no information about the schema definition is imported, only the objects contained within it.


The following is an example of using the SCHEMAS parameter. You can create the expdat.dmp file used in this example by running the example provided for the Export SCHEMAS parameter.

$ impdp hr/hr SCHEMAS=hr,oe DIRECTORY=dpump_dir1
     LOGFILE=schemas.log  DUMPFILE=expdat.dmp

The hr and oe schemas are imported from the expdat.dmp file. The log file, schemas.log, is written to dpump_dir1

Importing Only Particular Tables

The following example shows a simple use of the TABLES parameter to import only the employees and jobs tables from the expfull.dmp file. You can create the expfull.dmp dump file used in this example by running the example provided for the Full Database Export in Previous Topic.

$impdp hr/hr DIRECTORY=dpump_dir1 DUMPFILE=expfull.dmp TABLES=employees,jobs

This will import only employees and jobs tables from the DUMPFILE.

Running Data Pump Import Utility in Interactive Mode

Similar to the DATA PUMP EXPORT utility the Data Pump Import Jobs can also be suspended, resumed or killed. And, you can attach to an already existing import job from any client machine.

For Example, suppose a DBA starts a importing by typing the following command at one client machine CLNT1 by typing the following command

$impdp scott/tiger@mydb FULL=y DIRECTORY=data_pump_dir  
     DUMPFILE=full.dmp LOGFILE=myfullexp.log JOB_NAME=myfullJob

After some time, the DBA wants to stop this job temporarily. Then he presses CTRL+C to enter into interactive mode. He will get the Import> prompt where he can type interactive commands

Now he wants to stop this export job so he will type the following command

Are you sure you wish to stop this job ([y]/n): y

The job is placed in a stopped state and exits the client.

After finishing his other work, the DBA wants to resume the export job and the client machine from where he actually started the job is locked because, the user has locked his/her cabin. So now the DBA will go to another client machine and he reattach to the job by typing the following command

$ impdp hr/hr@mydb ATTACH=myfulljob

After the job status is displayed, he can issue the CONTINUE_CLIENT command to resume logging mode and restart the myfulljob job.


A message is displayed that the job has been reopened, and processing status is output to the client.

Note: After reattaching to the Job a DBA can also kill the job by typing KILL_JOB, if he doesn’t want to continue with the import job.



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Data Loader

Data Loader is a simple yet powerful tool to
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