It's OK to switch collocation on/off.

The setting only affects data that TSM is currently WRITING to tape.

If you turn collocation OFF, then any migration, move volume, or reclaim
tasks will write to an available tape in FILLING status, and as you guessed,
the "FILLING" tapes will all gradually fill up.

If you turn collocation back ON, then any migration, move volume, or reclaim
tasks will try to collocate the data they are writing.  That is, if the
process is moving data for CLIENT1, and there is a tape in FILLING status
that already contains data for CLIENT1, the process will mount and use that
tape.  OTHERWISE it will call for a SCRATCH tape, assuming you haven't
reached MAXSCRATCH  limit for the storage pool.  If you have already reached
the MAXSCRATCH limit for the storage pool, it looks for any existing tape in
FILLING status (I think it uses the least-full one, but I'm not sure about
that.)

Turning collocation back ON doesn't have any effect on data from past
backups that is not collocated, it just sits where it is on the existing
tapes.  However, your pool should eventually get (mostly) collocated again
over time by RECLAIM.





-----Original Message-----
From: Marc Lowers [mailto:Marc.R.Lowers AT GSK DOT COM]
Sent: Wednesday, November 20, 2002 10:21 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Switching Collocation on/off


I have collocation switched on our onsite tapepool at the moment, what are
the effects of switching this setting on and off.

I'm guessing that when switched off the volumes that are 'filling' will be
eventually used to 100%?

What will be the effects of then switching collocation back on?  Will new
volumes only then be used in the library for new backups?
Is data from past backups (from un-collocated backups) moved onto new
tapes or are only new backups set to collocate?


Marc.