You might want to look at turning colocation on but setting the maxscratch
parameter to the number of tapes you wish to "allocate" to that storage
pool. Perhaps 120-10-a few more for insurance.  ADSM will colocate as best
it can with those allocated tapes.

> ----------
> From:         Garin P. Walsh[SMTP:Garin_Walsh AT notes.sabre DOT com]
> Sent:         Monday, October 26, 1998 11:13 AM
> To:   ADSM-L AT VM.MARIST DOT EDU
> Subject:      Question about ensuring there is an available tape in a
> library for a database backup
>
> I hope this isn't a stupid question but I can't seem to find a way to
> achieve the following: I have 3595 L12 library with 2 drives and 120
> cartridges - all scratch. It is defined as a single device class to ADSM.
> Currently this is the device that the db backups are also being written
> to.
> I have in place a script to delete old backup volumes so that they don't
> consume all the volumes in the library so that there are scratch tapes
> available for migration from the backup storage pool. The system has been
> in place for 6 months now and is at about 80% capacity with 525 filespaces
> defined. My average restore times are getting too long now - about 10 to
> 15
> tape mounts on average for a full restore and I was thinking about turning
> collocation on to improve restore performance. My understanding of the
> process leads me to guess that the first nights incremental after doing
> this is going to consume the remaining scratch tapes - there are only a
> handful of tapes in a filling state and 100+ nodes get hit each night, the
> first night might not start spreading across additional tapes but the
> second night definitely would. My question is, how can I ensure that there
> are sufficient tapes available for the database backups with collocation
> on? Is it possible to define the L12 as two devices - one with 10 tapes
> and
> the other with 110, for instance, and use the 10 tape device for db
> backups
> and the 110 tape device for the migration destination?
>
> Thanks in advance for any suggestions
>
> Garin Walsh
> The Sabre Group
>