SQL> select * from v$flashback_database_log;
SQL> show parameter db_file
SQL> alter system set DB_RECOVERY_FILE_DEST_SIZE=2g;
System altered.
SQL> alter system set db_recovery_file_dest=’/rman/ora_flashback’;
System altered.
shutdown immediate;
startup mount;
SQL> alter system set db_flashback_retention_target=4320;
#for retaining for 3 days
System altered.
SQL> alter database flashback on;
Database altered.
SQL> alter database open;
Database altered.