This may help you.

"An option has been added to NetBackup to allow a robot with a media
access port to be automatically emptied and inventoried into the
NetBackup database."

http://seer.support.veritas.com/docs/236322.htm

Gregory, Gavin writes:
> Hello,
> 
> We are running an ATL7100 library and have started striking a problem now
> that it's nearly full.
> 
> If an operator inserts media thru the mailslots while there are tapes
> currently in the drives, the new volumes are sometimes moved to the
> temporarily empty slots that are still assigned in Netbackup to the media in
> the drives.  When the tape is removed from the drive the library attempts to
> return it to the same slot it was originally taken from, fails and downs the
> drive.
> 
> Is there a way around this without disabling the auto-insert on the library
> and moving the new media to known available slots?
> 
> Thanks, Gavin
> 
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-- 
Larry Kingery 
         "Robots should be RESPECTFUL."  -- Calvin, to Hobbes