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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

Managing REDO LOGFILES

Adding New Redo Logfile Group

Adding Members to group

Dropping Members from group

Dropping Logfile Group

Resizing Logfiles

Renaming or Relocating Logfiles

Clearing REDO 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

UNDO TABLESPACE

Switching to Automatic Management

Calculate Undo Retention

Altering UNDO Tablespace

Dropping an Undo Tablespace

Switching Undo Tablespaces

Viewing Information

SQL Loader

CASE STUDY (From MS-ACCESS to Oracle)

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 Utility

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)

Introduction

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

BACKUP AND RECOVERY

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

 

 

 

 

 

 

 

 

 

Taking online backups using RMAN   

To take online backups using RMAN the database must be running in ARCHIVELOG mode.

To take Full Database backup using RMAN do the following

Step 1

Assuming that the database is already running. Start RMAN by typing the following command

$ export ORACLE_SID=test
$ rman target system/manager nocatalog

Then RMAN will get connected to the database and it will show the following messages

RMAN connect to database

 

Step 2

Now to take Full database backup give the following command.

rman> backup database tag 'MyOnlineFullDBBackup';

The above command will take full database backup and it will store the backup in the directory mentioned in the DB_RECOVERY_FILE_DEST parameter

rman full online backup

You can specify TAG option to identify the backup. It is optional and if you want you can leave it. If you do not explicitly specify a tag with the TAG parameter of the BACKUP command, then RMAN implicitly creates a default tag for backups .

 The default format of the tag is TAGYYYYMMDDTHHMMSS,

Where

YYYY = year
MM = month
DD = day
HH = hour (24-hour format)
MM = minutes
SS = seconds

In this article we have learnt how to take backup of full database. By default RMAN takes the backup as BACKUPSETS i.e. it combines of multiple datafiles into one backupset.

And in backupset RMAN just backups the occupied blocks of each datafile leaving aside empty blocks.

For example, if you have a datafile 'users.dbf' of size 500M and in this file the data is only upto 300M and 200M is empty, then when you take the backup of this file as backupset, RMAN will only copy 300M leaving aside empty blocks. Thus in this way the backup size will be small and it will take less time also.

 

Taking backup of archive log files along with Full Backup

You can also take the backup of archive log files along with the full database by giving the following command

RMAN> BACKUP DATABASE PLUS ARCHIVELOG;

The above command backs up the database, switches the online redo logs, and includes archived logs in the backup

 

Instead of creating backupsets you can also ask RMAN to take IMAGE backups. Image backups means copy the datafile as it is. Follow the link for more information How to take image backups in RMAN

Similarly you can also take partial backups of particular tablespaces or particular datafiles. How to take online backup of particular tablespaces or datafiles

 

 


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