If you are in a pure TSM environment, meaning the VTL is exclusively
used by TSM, how useful is truncating scratch tapes and returning that
space to the VTL's pool of free space?  Unless you use co-location all
volumes are going to be quickly written to their define maximum native
capacity.  The only exception to that would be TSM db backup volumes.
For me, the VTL's short mount/dismount times and using a small size
(10GB) for the defined maximum native capacity has meant I do not
require co-location.  Since my volumes are small even a TSM db backup
would not produce much "wasted" space.  

So while it is an interesting behavior, in the above environment, how
relevant is it?

Thanks,
H. Milton Johnson
-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Curtis Preston
Sent: Friday, June 15, 2007 4:19 PM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: [ADSM-L] How to Incorporate a CDL into a TSM environment?

John Schneider said:
>I can't speak for everybody's product out there, but the EMC CDL (EDL) 
>releases the used pages from the virtual volume as soon as you begin to

>overwrite the virtual volume from the beginning.  One thing that does 
>this is a Label Libvolume.

This is the way they all work.  And you're right.   All you have to do
is find new tapes in the scratch pool and label them, and voila!.  OR...
You can just wait for the tape to get reused by TSM, at which point all
its space will get erased then replaced with whatever you write to it
next.