How to enable/disable Flashback in oracle database 11g

How to enable Flashback in oracle database 11g

1. Database has to be in ARCHIVELOG mode.

    

 Change ARCHIVELOG mode of database

2. Flash Recovery Area has to be configured. To configure PFB steps

SQL> show parameter db_recovery_file_dest

NAME                            TYPE           VALUE

-------------------------       -----------    ----------------------

db_recovery_file_dest             string

db_recovery_file_dest_size     big integer     0

Currently flashback is disabled. To enable

A. Set db_recovery_file_dest_size initialization parameter.

SQL> alter system set db_recovery_file_dest_size=2g;

System altered.

B. After db_recovery_file_dest_size parameeter has been set, create a location in OS where your FLASHBACK logs will be stored.

bash-3.2$ cd /FRA

bash-3.2$ mkdir FLASHBACK

bash-3.2$ pwd

/FRA/FLASHBACK

C. Now set db_recovery_file_dest initialization parameter.

SQL> alter system set db_recovery_file_dest='/FRA/FLASHBACK';   

System altered.

SQL> show parameter db_recovery

NAME                     TYPE                VALUE

-------------------      -----------         -----------------------

db_recovery_file_dest            string           /FRA/FLASHBACK

db_recovery_file_dest_size     big integer    2G

3. Create an Undo Tablespace with enough space to keep data for flashback operations. More often users update the database more space is required.

 

4. By default automatic Undo Management is enabled, if not enable it. In 10g release 2 or later default value of UNDO management is AUTO. If you are using lower release then PFB to enable it:-

SQL> alter system set undo_management=auto scope=spfile;

System altered

5. Shut Down your database

SQL> shu immediate;

Database closed.

Database dismounted.

ORACLE instance shut down

6. Startup your database in MOUNT mode

SQL> startup mount;

ORACLE instance started.

Total System Global Area 1025298432 bytes

Fixed Size                  1341000 bytes

Variable Size             322963896 bytes

Database Buffers          696254464 bytes

Redo Buffers                4739072 bytes

Database mounted.

7. Change the Flashback mode of the database

SQL> select flashback_on from v$database;

FLASHBACK_ON

------------------

NO

SQL>alter database flashback ON;

Database altered.

SQL> select flashback_on from v$database;

FLASHBACK_ON

------------------

YES

SQL> alter database open;

Database altered.

FLASHBACK mode of the database has been enabled.

How to disable FLASHBACK in Oracle Database 11G R1 and below versions

1. Shut Down your database

SQL> shu immediate;

Database closed.

Database dismounted.

ORACLE instance shut down

2. Startup your database in MOUNT mode

SQL> startup mount;

ORACLE instance started.

Total System Global Area 1025298432 bytes

Fixed Size                  1341000 bytes

Variable Size             322963896 bytes

Database Buffers          696254464 bytes

Redo Buffers                4739072 bytes

Database mounted.

SQL> select flashback_on from v$database;

FLASHBACK_ON

------------------

YES

SQL>alter database flashback OFF;

Database altered.

SQL> select flashback_on from v$database;

FLASHBACK_ON

------------------

NO

SQL> alter database open;

Database altered.

FLASHBACK mode of the database has been disabled.

How to enable/disable FLASHBACK in Oracle Database 11G R2 and above versions.

 

From 11GR2 we do not have to bounce the database to alter flashback.

1. Database has to be in ARCHIVELOG mode.

     To change ARCHIVE mode refer to -- Change ARCHIVE mode of database

 

2. Flash Recovery Area has to be configured. To configure PFA steps.

 

3.  TO enable or disable flashback , we can change this while database is in open mode. PFB

SQL> select open_mode from v$database;

OPEN_MODE

--------------------

READ WRITE

SQL> select flashback_on from v$database;

FLASHBACK_ON

------------------

NO

SQL> alter database flashback on;

Database altered.

SQL> alter database flashback off;

Database altered.