This is not elegant but it does the job.  I suspect you may have moved on from 
this issue quite some time ago.

I use this script for Veritas NetBackup 6.5.6 installation with a VTL library 
and a physical library.

First I navigate to the installation directory\volmgr\bin directory
cd\
cd ?Program Files"\Veritas\volmgr\bin?

Next I create a list of tapes in the Scratch pool

vmquery -pn Scratch -l>c:\scratchlist.txt  

(Note: The name of the pool is Case-sensitive so be sure you list the pool the 
way it shows up in Veritas)

Finally I run a FOR loop command using the file just created above.

for /f %a in (c:\scratchlist.txt) do C:\"Program 
Files"\Veritas\netbackup\bin\admincmd\bplabel -m %a -d hcart -o -p Scratch 
-host mediaserver -erase

I have schedule this CMD file to run daily to reclaim the VTL disk space for 
the expired media.  The above information was gleaned from other online 
submissions but I have added a few clarifying comments that should help 
implementation, especially for folks just starting out with this issue.

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