Dunno if this is relevant in your case but I'll share it anyway..Netbackup should get rid of the cache files once the backup has finished. we had a massive problem where large VSP .tmp cache files were remaining on the drives after the backups finished, they'd be locked (by the system process) and couldn't be deleted (file in use). The drives were eventually filling up with old cache files causing major user issues. The only way to delete them was to delete the handle on the file by using Process Explorer (free download, search Google) to remove the lock (or by just rebooting the server), then deleting.
We discovered it was because of McAffee's AV realtime scanning...once we put in an exlusion to stop scanning any *.tmp files in the root of any drive, hey presto, no more cache files filling up drives.