Yes, but that is the essence of the os390 operating system.
It shares resources virtually, to get the best use from them.
With sequential devices like tapes, which it is not practical to interrupt, you
need to ensure that the virtual demand is not too far out of line with the real
resource (number of tape drives).
OS390 production lpars are normally tightly controlled, you should not see
unexpected demand for tape, and  you should be able to achieve this balance for
the most part by attention to scheduling of TSM processes that use tapes, so
that they occur at times when the demand from non TSM tasks for tapes is low.
If best efforts still mean you cannot meet the demand, and you cannot reduce it,
then you have
to increase the resource, but this applies equally to dedicated TSM systems.







Bill Boyer <bill.boyer AT verizon DOT net> on 05/22/2002 06:41:08 PM

Please respond to "ADSM: Dist Stor Manager" <adsm-l AT vm.marist DOT edu>

To:   adsm-l AT vm.marist DOT edu
cc:    (bcc: John Naylor/HAV/SSE)
Subject:  Re: yes/no tape question



If you have several Z-boxes or LPARS sharing the tape drives...You would
have some offline when they are online to other systems. Unless you're in a
Sysplex.... This was where we would get bit. The TSM server wasn't on the
'production' LPAR and the operator would vary the drives offline and online
to the production LPAR leaving only 1 or 2 drives for TSM. Plus DFSHShsm was
on this LPAR...primary and secondary space management took up drives... Even
if you have only those physically attached drives defined in HCD,you can end
up with tape drive allocation due to other processes and users using the
drives. Unless you can dedicate drives and an LPAR/Z-box just to TSM,
there's always the possibility of a drive not being available. You get some
DFU running a big SAS program using 5-tape drives....the words justifiable
homicide comes to mind! :-)

Bill Boyer
DSS, Inc.
"Backup my harddrive...how do I put it in reverse?" - ??