Hi,
Update the Tape Drive/Autoloader firmware to the latest available
Try to Clean,Erase and Change the Media Tape and fire a backup job.
Update the Veritas device driver to the latest:
http://seer.support.veritas.com/docs/275676.htm
Refer the following document:
http://seer.support.veritas.com/docs/192216.htm
Also check system log for event id 7,9, 11 or 15.
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