On 1/31/2012 9:07 AM, Hervey Martinez wrote:
3 weeks ago we implemented HSM's CRQ and immediately after doing so, we
experienced a jump in our tape usage. After a week of this unexplained tape
growth, I added the default PARTIALTAPE(REUSE) parm to HSM and at that point
our unexplained tape growth stopped.
I opened a ticket with IBM and they have not been able to give me an explanation other than
"somebody must have done a PARTIALTAPE(MARFULL)"; Also, they have not been able to
explain how come our tape growth stopped once I added the "PARTIALTAPE(REUSE)" -the
default.
I read something about cross memory region, CSSXMODE(Y/N), might be the culprit
in this situation but IBM denies any issues with this.
Has anybody experienced anything like this before?
Regards,
Hervey Martinez
Hervey,
What IBM told you here is true. PARTIALTAPE(MARKFULL) uses more tapes
because HSM marks the tape full after every space management cycle. On
the next space management cycle, HSM mounts a scratch tape, even if the
tape used previously still has space on it. PARTIALTAPE(MARKFULL) is an
old parm primarily used to make manual tape library operations easier.
It allowed HSM to just grab the next scratch tape in the autoloader,
without waiting for the operator to retrieve the tape from the library.
In today's large capacity tape, automated library environment,
PARTIALTAPE(REUSE) makes much more sense. The library will
automatically mount the large cap tape, and HSM will just MOD on to the
end of it, instead of using another tape. If you did an HSM Q STATUS
before changing PARTIALTAPE back to REUSE, you should have seen the
MARKFULL there.
CSSXMODE is a parm you can use to allow HSM to grow horizontally by
allocating an address space for each DFDSS task running under HSM (as
opposed to jamming all the concurrent DFDSS tasks into the one HSM
address space). It's primary purpose is for virtual storage constraint
relief, and has nothing at all to do with tape usage.
Regards,
Tom Conley
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