How to Enable/Configure and Disable Flashback (On/Off) Feature in Oracle

Pre-requesites:
a. Database must in archivelog mode.
b. Automatic undo tablespace management must be on
c. There should be enough space (depends on your requirement) in undo tablespace.
Steps
1. Verify the flashback feature is on or not using the flashback_on column in the v$database

Listener Not Starting: IBM/AIX RISC System/6000 Error: 1: Not owner TNS-12555, TNS-12560, TNS-00525

Problem Description: lsnrctl start command failing with following error message

> lsnrctl start

LSNRCTL for IBM/AIX RISC System/6000: Version 11.2.0.3.0 - Production on 12-AUG-2014 17:15:10

Copyright (c) 1991, 2011, Oracle. All rights reserved.

Starting /oracle/DWR/112_64/bin/tnslsnr: please wait...

TNSLSNR for IBM/AIX RISC System/6000: Version 11.2.0.3.0 - Production

Fix ORA-30052: invalid lower limit snapshot expression

Error Description:
Oracle flashback transaction version query failing with following error message.
SQL> SELECT *
FROM dept
VERSIONS BETWEEN TIMESTAMP
      TO_TIMESTAMP('2014-07-14 14:12:00')
  AND TO_TIMESTAMP('2014-07-14 14:26:01')   ;
FROM dept
     *
ERROR at line 2:
ORA-30052: invalid lower limit snapshot expression