Prod Concurrent is behaving very badly - Queue/Pending Standby state upto 700+

Dear Legends,

Environment: Apps - R12.1.3 DB - 11.1.0.7 Multi Node - Non RAC

Issue:

Concurrent Requests are queued up Suddenly to or more 750 or 1400 + requests for some or more users.

Standard Manager Process - 20 Sleep - 30 Cache Size - 30

Change:

No change has been done in System.

DB Parameters:

job_queue_process - 20

Internal Manager Log:

Output file size:

150047322

+------------- 1) PUBLISH -------------+

Beginning post-processing of request 16573394 on node PROD_DB at 03-AUG-2016 10:22:45.

APP-FND-01564: ORACLE error 3113 in publish

Cause: publish failed due to ORA-03113: end-of-file on communication channel.

The SQL statement being executed at the time of the error was: &SQLSTMT and was executed from the file &ERRFILE.