> While I find that RMAN backup configured by the DBA has completed
> sucessfully, the RMAN logs tell a different story.

First, have your DBA demonstrate a successful RMAN backup to a channel
of type "disk," which requires only two RMAN commands totalling seven
words.  That will have no NetBackup involvement whatsoever.  Don't worry
about NetBackup until you get this working.

Once you can back up to disk, use the Troubleshooting section of the
NetBackup for Oracle System Administrator's Guide.  It will lead you to
the problem in a logical fashion.

> Also would like to know how to limit the RMAN streams, in our 
> case we sould
> have arnd 27-30 active streams per RMAN policy we fire.

That doesn't make any sense.  The number of NetBackup streams RMAN
requests is controlled by how many channels your RMAN script allocates.
If your DBA allocates 30 channels, you need a new DBA.