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

When running SQL loader concurrent request, we are seeing below error.

Error:

SQL*Loader-128: unable to begin a session

ORA-01017: invalid username/password; logon denied

SQL*Loader: Release 10.1.0.5.0 - Production on Wed Jun 24 14:08:27 2020

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SQL*Loader-128: unable to begin a session

ORA-01017: invalid username/password; logon denied

Program exited with status 1

Concurrent Manager encountered an error while running SQL*Loader for your concurrent request 57822615.

Cause:

Service Manager logfile (for all managers started by FNDSM). This causes FNDSM log to grow to enormous size 2 GB

$ du -sh FNDSM2342760.mgr

2.1G    FNDSM2342760.mgr

Workaround:

Workaround 1: Restart Concurrent Managers

Workaround 2: Take backup of the file and nullify the file to reduce the size.

$ >FNDSM2342760.mgr

Also you can refer below Oracle Doc for more details and other solution

Concurrent Requests fail with SQL*Loader-101: Invalid Argument for username/password (Due to FNDSM Log File Size Grows 2 GB ) (Doc ID 1542216.1)