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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










Using Oracle Import Tool

Using Import Utility

Objects exported by export utility can only be imported by Import utility. Import utility can  run in Interactive mode or command line mode.

You can let Import prompt you for parameters by entering the IMP command followed by your username/password:

     Example: IMP SCOTT/TIGER

Or, you can control how Import runs by entering the IMP command followed

by various arguments. To specify parameters, you use keywords:

     Format:  IMP KEYWORD=value or KEYWORD=(value1,value2,...,valueN)


               or TABLES=(T1:P1,T1:P2), if T1 is partitioned table

USERID must be the first parameter on the command line.


Description (Default)




size of data buffer


input files (EXPDAT.DMP)


just list file contents (N)


ignore create errors (N)


import grants (Y)


import indexes (Y)


import data rows (Y)


log file of screen output


import entire file (N)


list of owner usernames


list of usernames


list of table names


length of IO record


incremental import type


commit array insert (N)


parameter filename


import constraints (Y)


overwrite tablespace data file (N)


write table/index info to specified file


skip maintenance of unusable indexes (N)


display progress every x rows(0)


skip validation of specified type ids


maximum size of each dump file


import precomputed statistics (always)


suspend when a space related error is encountered(N)


text string used to identify resumable statement


wait time for RESUMABLE


compile procedures, packages, and functions (Y)


import streams general metadata (Y)


import streams instantiation metadata (N)

Example Importing Individual Tables

To import individual tables from a full database export dump file give the following command

$imp scott/tiger FILE=myfullexp.dmp FROMUSER=scott TABLES=(emp,dept)

This command will import only emp, dept tables into Scott user and you will get a output similar  to as shown below

Export file created by EXPORT:V10.00.00 via conventional path
import done in WE8DEC character set and AL16UTF16 NCHAR character set
. importing SCOTT's objects into SCOTT
. . importing table                         "DEPT"          4 rows imported
. . importing table                          "EMP"         14 rows imported

Import terminated successfully without warnings.

Example, Importing Tables of One User account into another User account

For example, suppose Ali has exported tables into a dump file mytables.dmp. Now Scott wants to import these tables. To achieve this Scott will give the following import command

$imp scott/tiger  FILE=mytables.dmp FROMUSER=ali TOUSER=scott

Then import utility will give a warning that tables in the dump file was exported by user Ali and not you and then proceed.

Example Importing Tables Using Pattern Matching

Suppose you want to import all tables from a dump file whose name matches a particular pattern. To do so, use “%” wild character in TABLES option. For example, the following command will import all tables whose names starts with alphabet “a” and those tables whose name contains alphabet “d”

$imp scott/tiger FILE=myfullexp.dmp FROMUSER=scott TABLES=(a%,%d%)

Migrating a Database across platforms.

The Export and Import utilities are the only method that Oracle supports for moving an existing Oracle database from one hardware platform to another. This includes moving between UNIX and NT systems and also moving between two NT systems running on different platforms.

The following steps present a general overview of how to move a database between platforms.

  1. As a DBA user, issue the following SQL query to get the exact name of all tablespaces. You will need this information later in the process.

SQL> SELECT tablespace_name FROM dba_tablespaces;

  1. As a DBA user, perform a full export from the source database, for example:

$ exp system/manager FULL=y FILE=myfullexp.dmp

  1. Move the dump file to the target database server. If you use FTP, be sure to copy it in binary format (by entering binary at the FTP prompt) to avoid file corruption.
  2. Create a database on the target server.
  3. Before importing the dump file, you must first create your tablespaces, using the information obtained in Step 1. Otherwise, the import will create the corresponding datafiles in the same file structure as at the source database, which may not be compatible with the file structure on the target system.
  4. As a DBA user, perform a full import with the IGNORE parameter enabled:

$ imp system/manager FULL=y IGNORE=y FILE=myfullexp.dmp

Using IGNORE=y instructs Oracle to ignore any creation errors during the import and permit the import to complete.

  1. Perform a full backup of your new database.



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Data Loader is a simple yet powerful tool to
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