The message you have posted has not been generated by NetWorker. For a backup 
to disk in NW you must configure a (Advanced) File Type Device which is 
directory, not a file. 

However, the message could have been generated during a pre-backup phase where 
  1. 'the application' generates a backup to file before it is then
  2. getting copied by the backup application (NetWorker)
In this case you better look at the initiating software as the error obviously 
happens during the first step.

For EMC Celerra issues there might be better communities where you want to 
seach.

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