SQL*Loader-128: unable to begin a session ORA-01017: invalid username/password; logon denied

Error:
Programs were erroring out with below error.
Arguments
------------
/u01/prod/attach/1418160319478.txt
------------
ORA-01017: invalid username/password; logon denied
SQL*Loader-704: Internal error: ulconnect: OCISessionBegin [-1]

SQL*Loader: Release 8.0.6.3.0 - Production on Tue Dec 9 22:59:13 2014

(c) Copyright 1999 Oracle Corporation.  All rights reserved.

ORA-01017: invalid username/password; logon denied
SQL*Loader-704: Internal error: ulconnect: OCISessionBegin [-1]

Program exited with status 1
Concurrent Manager encountered an error while running SQL*Loader for your concurrent request 140568679.

Review your concurrent request log file for more detailed information.


+---------------------------------------------------------------------------+
Executing request completion options...

Sol:
When we started trouble shooting we found below points.

- Parameter processes it has been changed from 1528 to 2000 in the init.ora file
- FNDSM log file is below the 2GB.
- The program hasn't been scheduled by an ended user ( Bug 12896168 )
- Instance is using it's own service name (Doc ID 1160553.1)
- Program executable permissions have been check
- Issue occurs in RAC and non RAC environments  

For our issue it was caused by the size of the FNDSM log which was over 2GB.
-rw-r--r--    1 appp14   oaa      2147483647 Dec  9 21:15 FNDSM257792.mgr

To fix the issue, we have truncated the file.
>   FNDSM257792.mgr

After that user ran the program and it got completed successfully.