Oracle Enable flashback

Below are the steps to enable flashback on 

1. Set up these parameters db_recovery_file_dest and db_recovery_file_dest_size
2. Put the database in archive log mode.
3. Issue command alter database flashback on;

Steps done by me:

SQL> select FLASHBACK_ON from v$database;
FLASHBACK_ON
------------------
NO
SQL>
SQL> show parameter db_recovery
NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
db_recovery_file_dest                string      +FRA
db_recovery_file_dest_size           big integer 12G
SQL> archive log list
Database log mode              Archive Mode
Automatic archival             Enabled
Archive destination            USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence     196
Next log sequence to archive   197
Current log sequence           197
SQL>
SQL> alter database flashback on;
Database altered.
SQL> select FLASHBACK_ON from v$database;
FLASHBACK_ON
------------------
YES
SQL>

To put physical standby database in flashback mode we have to stop the real time apply and then do it :

SQL> select FLASHBACK_ON from v$database;
FLASHBACK_ON
------------------
NO
SQL> select open_mode from v$database;
OPEN_MODE
--------------------
READ ONLY WITH APPLY
SQL> alter database flashback on;
alter database flashback on
*
ERROR at line 1:
ORA-01153: an incompatible media recovery is active

SQL>
SQL> alter database recover managed standby database cancel;
Database altered.
SQL> select open_mode from v$database;
OPEN_MODE
--------------------
READ ONLY
SQL>
SQL> alter database flashback on;
Database altered.
SQL> alter database recover managed standby database using current logfile disconnect;
Database altered.
SQL> select open_mode from v$database;
OPEN_MODE
--------------------
READ ONLY WITH APPLY
SQL> select FLASHBACK_ON from v$database;
FLASHBACK_ON
------------------
YES
SQL>