First - welcome to ADSM!

I think, from reading your posting, that you have a very accurate
understanding of how ADSM handles the off-site tapes.  We have a very similar
setup, although we took an extra step - we only collocate our server backups;
we do not collocate our desktop backups.  In the DR pool, neither pool is
collocated.  It is the tradeoff that you are trying to manage - the number of
tapes involved, vs. the actual number of times that they will get mounted.
Obviously, the hope here is that they never will be mounted, but if they are,
then the potential for lots of mounts is as you described it.

The problem, though, is not quite as bad as it sounds.  When you copy a
collocated tape, the files of course stay together, and so a copypool tape of
a collocated tape, even though the backup pool is not collocated, should
retain a fair amount of the "togetherness" of a user's files.  I am not sure
about the backup of a diskpool to tape, but would not expect the same kind of
results.  So it would depend on where your data is when it is backed up - if
it is on tape, then it's not so much of a problem, while if it's on disk, then
you get a random order (I think).

We had similar concerns when we took collocation off of our desktop machines.
We were concerned because each customer had at least one partially filled tape
it was getting to be a significant number of volumes, so we turned it off.
We rationalized the fragmentation issue by understanding how ADSM moves data
from the disk pool to tape.  It moves all of one user, and then another, until
it gets below the low threshold.  Thus, data from a client may sit on disk for
many days until he becomes a significant user, and then all of the files are
moved together to tape, thus still keeping things together as such.  Of course
each time you move you will get a different tape, but it probably isn't as bad
as every night you get a few files on a new tape.....

Hope this helps.

Jerry Lawson
jlawson AT itthartford DOT com
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Author: INTERNET.OWNERAD
Subject: Offsite DR Cartridges
01-27-97 10:14 AM

        We are a new ADSM shop using MVS as a server (2.1.0.10) and TLMS as
     our tape management system.  We colocate our onsite primary pool, but
     not our offsite copypool.  Onsite restores have been quite smooth, but
     we fear that a DR situation would pose some issues (the number of
     cartridges needed to restore a single server could be excessive).
        Is there anyone out there using offsite colocation?  Or is there
     any way to keep less data in the offsite copypool (just keep active
     files)?
        Also, for a DR test or in the case of media failure, there doesn't
     seem to be any way to find out what cartridges would be needed to
     restore a specific node or filespace.  Can anyone shed some light?
        Thanks for your help.

                 Jim Kleberg, State Street Bank  617-985-8392