RMAN backups not showing as unsuccessful in job logs

Hi all,

Back again with another NetWorker and RMAN query.

I recently created a client definition for an RMAN backup, and duly put in the location of the nsr_rman file in the backup command field. 

Our Oracle team have supposedly carried out all the script editing in order for schedule RMAN backups to work, however no RMAN backup logfiles are created.  The backup doesn't actually appear to work, however there is no evidence of this in the NetWorker job log - it shows as successful.

The only log entry in NetWorker is the following:

stty:  standard input: Invalid argument

find: /tmp/rman.ksh.work/745.tmp: No such file or directory

However the Oracle team came back with quite a long error message when the backup tried to run:

RMAN-03023: executing command: SET COMMAND ID

RMAN-03090: Starting backup at 22/03/2012 09:00:00

RMAN-03033: current log archived

RMAN-00571:====================================================================

RMAN-00569:===============ERROR MESSAGE STACK FOLLOWS ========================

RMAN-00571:=====================================================================

RMAN-03002: failure of backup plus archivelog command at 22/03/2012 09:00:00

ORA-19554: error allocating device, device type: SBT_TAPE, device name:

ORA-27211: Failed to load Media Management Library

Additional information: 2

Recover Manager complete:

The backup mechanism does indeed work; filesystem backups for this client work fine and other RMAN backups to this NetWorker server also work fine. 

It is just this particular client and it's instances that won't back up correctly.

Any suggestions as to where I can look?

Thanks!