[Veritas-bu] Media/Image expiration process?

This is a note I sent to Veritas tech support. If anyone here knows the answer 
though, all the better/faster.
***
I'm running NB-3.2 on Solaris-2.7 servers.  I have a backup class with a user 
backup schedule set with a retention level of 1, which corresponded to 2 
weeks.  I ran a backup of some files, from a workstation.  The files were 
backed up fine.

I ran the backup on 7/6/2000 at 10:06 AM.

I figured out the backup_id from the catalog.

On the master server, I ran a 

bpexpdate -backupid BACKUPID -d '07/06/2000 12:00:00'

When I then queried the image catalog using bpimagelist, my backup had an 
updated time of expiration, set for the time I'd used in the bpexpdate command.

If however, I check the media that the backup was written to, I show the media 
as still being assigned, even though the backup image itself has expired from 
the catalog. I can check the media contents with the GUI, or by running

bpmedialist -mcontents -ev A0046A

It returns:

File number 1
  Backup id = clio.pprd.abbott.com_0962833049
  Creation date = 07/05/00 16:37:
  Expiration date = 07/19/00 16:37:
  Retention level = 1
  Copy number = 1
  Fragment number = 1
  Fragment size (in bytes) = 32768
  Data start byte offset = 3072
  Block size (in bytes) = 262144

File number 2
  Backup id = clio.pprd.abbott.com_0962895966
  Creation date = 07/06/00 10:06:
  Expiration date = 07/20/00 10:06:
  Retention level = 1
  Copy number = 1
  Fragment number = 1
  Fragment size (in bytes) = 32768
  Data start byte offset = 37888
  Block size (in bytes) = 262144

Both of these images are gone from my catalog however.

Can you explain why this media is still allocated/assigned, even though the 
images on the media have expired?  What routine process runs to purge/expire 
old media?

Thanks.

-- 
Andy Steingruebl              | e-mail: steingra AT pprd.abbott DOT com         
 
Unix Systems Admin/Programmer | phone:  (847) 935-4728                    
Unix/Network Security         | fax:    (847) 935-0142                    
Abbott Laboratories, PPDR&D   | post:   100 Abbott Park Road, D472 - AP9A
                              |         Abbott Park, IL 60064-6115