FLASHBACK

SQL> select flashback_on from v$database;

FLASHBACK_ON

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

NO

SQL> alter database flashback ON;

alter database flashback ON

*

ERROR at line 1:

ORA-38759: Database must be mounted by only one instance 

and not open.

SQL> shut immediate;

Database closed.

Database dismounted.

ORACLE instance shut down.

SQL> startup mount;

SQL> alter database flashback ON;

alter database flashback ON

*

ERROR at line 1:

ORA-38706: Cannot turn on FLASHBACK DATABASE logging.

ORA-38707: Media recovery is not enabled.

SQL> alter database archivelog;

Database altered.

SQL> alter database flashback ON;

Database altered.

SQL> select flashback_on from v$database;

FLASHBACK_ON

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

YES

4)Open the database and optionally you can set 

DB_FLASHBACK_RETENTION_TARGET to the length of the 

desired flashback window in minutes. By default it 

is 1 day(1440 minutes).

SQL> ALTER DATABASE OPEN;

To make it 3 days

SQL> alter database open;

Database altered.

SQL> alter system set db_flashback_retention_target=4320;

System altered.

SQL> show parameter db_flashback_retention_target

NAME                                 TYPE        VALUE

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

db_flashback_retention_target        integer     4320