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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










Managing Availibility of Tablespaces in Oracle

Taking tablespaces Offline or Online

You can take an online tablespace offline so that it is temporarily unavailable for general use. The rest of the database remains open and available for users to access data. Conversely, you can bring an offline tablespace online to make the schema objects within the tablespace available to database users. The database must be open to alter the availability of a tablespace.

We usually take tablespaces offline for maintenance purposes.

To alter the availability of a tablespace, use the ALTER TABLESPACE statement. You must have the ALTER TABLESPACE or MANAGE TABLESPACE system privilege.

To Take a Tablespace Offline give the following command

SQL>alter tablespace ica offline;

To again bring it back online give the following command.

SQL>alter tablespace ica online;

To take individual datafile offline type the following command

SQL>alter database datafile ‘/u01/oracle/ica/ica_tbs01.dbf’ offline;

Again to bring it back online give the following command

SQL> alter database datafile ‘/u01/oracle/ica/ica_tbs01.dbf’ online;

Note: You can’t take individual datafiles offline it the database is running in NOARCHIVELOG mode.  If the datafile has become corrupt or missing when the database is running in NOARCHIVELOG mode then you can only drop it by giving the following command

SQL>alter database datafile ‘/u01/oracle/ica/ica_tbs01.dbf’ offline for drop;

Making a Tablespace Read only.

Making a tablespace read-only prevents write operations on the datafiles in the tablespace. The primary purpose of read-only tablespaces is to eliminate the need to perform backup and recovery of large, static portions of a database. Read-only tablespaces also provide a way to protecting historical data so that users cannot modify it. Making a tablespace read-only prevents updates on all tables in the tablespace, regardless of a user's update privilege level.

To make a tablespace read only

SQL>alter tablespace ica read only

Again to make it read write

SQL>alter tablespace ica read write;

Renaming Tablespaces

Using the RENAME TO clause of the ALTER TABLESPACE, you can rename a permanent or temporary tablespace. For example, the following statement renames the users tablespace:


The following affect the operation of this statement:

Dropping Tablespaces

You can drop a tablespace and its contents (the segments contained in the tablespace) from the database if the tablespace and its contents are no longer required. You must have the DROP TABLESPACE system privilege to drop a tablespace.

Caution: Once a tablespace has been dropped, the data in the tablespace is not recoverable. Therefore, make sure that all data contained in a tablespace to be dropped will not be required in the future. Also, immediately before and after dropping a tablespace from a database, back up the database completely

To drop a tablespace give the following command.

SQL> drop tablespace ica;

This will drop the tablespace only if it is empty. If it is not empty and if you want to drop it anyhow then add the following keyword

SQL>drop tablespace ica including contents;

This will drop the tablespace even if it is not empty. But the datafiles will not be deleted you have to use operating system command to delete the files.

But If  you include datafiles keyword then, the associated datafiles will also be deleted from the disk.

SQL>drop tablespace ica including contents and datafiles;




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