If collocation is on now, then each tape belongs to a specific server. If
you turn it off, then TSM gets the least filling volume first to put data
on even if the data belongs to another server. Makes for more efficient use
of the tapes but then you could have data from multiple servers on one
volume. Could result in many mounts for a restore of a server. If you turn
collocation back on, then TSM will use those volumes and make them belong
to the last server that had data wrote to them I believe. Then when those
volumes get full, it starts with new volumes for each server that it needs
and keeps only that servers data on that volume. The tapes that have
multiple servers on them do not get moved to other tapes unless you perform
a move data on them or move them back to the disk storage pool and then
migrate back to tape. Then TSM will collocate properly again.

Thanks,
Robert Rippy



From: Marc Lowers <Marc.R.Lowers AT GSK DOT COM> on 11/20/2002 10:21 AM

Please respond to "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>

To:   ADSM-L AT VM.MARIST DOT EDU
cc:
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.