Hello Jim...
If a volume originally came from scratch into a stgpool, you will notice
that "Scratch Volume?:" says yes for a 'q vol'.  Maxscratch sets that
maximum number of such volumes in a stgpool.  For example, if you set
maxscratch to 10 on a stgpool that originally has no volumes, then when
it needs a volume the server will take a libv in the library that is
marked as scratch, define it into the stgpool, change the libv to
private, and the number of "volumes that came from scratch" is 1, which
is less than the 10 you set.  This can happen 9 more times.  When there
are 10 tapes, the next time it needs a tape (all ten have reached end of
tape and are marked full) you will get an out-of-storage error.  The
stgpool will be full.  If you increase maxscratch to 20 then, then it
can grab 10 more tapes.  If you are at 7 tapes obtained from scratch and
one gets reclaimed, then the number of "volumes that came from scratch"
or volumes for which "Scratch Volume?:" is true decreases to 6.
The volume gets deleted from the stgpool, and the libv gets changed from
private to scratch and is available for any stgpool in that library.

Note that if _you_ explicitly define a volume into a stgpool with the
def vol command, then "Scratch Volume?:" is "no" and it does not count
towards the maxscratch.  Note also that when such a volume fills, has
data expire, and is reclaimed, it simply goes back to Empty status and
is not available for other stgpools.  It is, however available for the
stgpool in which it is defined.

Hope this helps...
Bruce
"Zopolis, Jim (TechServ)" wrote:
>
> I have a question about the "maximum scratch volumes allowed"
> parameter. I understand that this parameter is always incremented,
> never decremented when a tape is returned to the scratch pool.
>
> How do you know when to increase the max scratch volumes
> parameter ?
>