My specific problem is with a tape pool that is a target for virtual volumes 
created by a remote TSM server. The number of cartridges in use by the pool 
goes up and up, at a faster rate than the data growth on the remote server. I 
suspect there are many virtual volumes in the target pool with not many active 
files left on them. 

My understanding is that even one active file in a virtual volume keeps all the 
space used by it on a tape from being reclaimed. So far, my only resort seems 
to be to do MOVE DATA on virtual volumes with log pct_utilization, using 
'reconstruct=yes'. That won't be efficient or fast. 

If I am missing something, please let me know.

My thanks to all who have offered suggestions so far,
Keith