On Dec 27, 2005, at 7:32 AM, Chris Mason wrote:
I haven't really been paying very much attention to this topic
since it's
not at all my forte - if anything is. However, I'm struck by the
seeming
fact that there is no current general solution to the tape set-up
problem.
If there were and some users were allowed to use the required
procedure and
some users weren't then there would be a solution also to the
subject line.
I remember many years ago when I submitted a job involving
typically tape
mounting - there was a time when disks could be mounted per job
also - then
I had to include a JES2 card - I vaguely remember. The card had to
mention
in text suitable for an operator rather than a program which tape
volumes
the job would require. I think the presence of the card caused the
job to be
held so that the operator could release it presumably when both the
tape
drives and the tapes from the library were available.
That was the state of play about 20 years ago I guess and I'm
surprised
there's not a more solid solution about now - or maybe there is but,
somehow, it can't be used to block use of it by a particular user.
Chris Mason
Chrism,
If you mean "automatically" system code., then I agree with you. The
user code (that I wrote) is invoked at each mount request.
The decision to cancel has to be done within user written code. Each
installation has to make their own mind up whether to cancel the job
or not.
I could just see if IBM came up with a process there would still have
to be "rules" if not then the user community would be lobbying IBM to
have an exit so they could decide.
Some installations may or may not care less about tape mounts. Each
installation would then have to create rules unique to their
installation.
With robotic tape mechanisms mounting tape is probably costs less so
in some situations it maybe almost irrelevant. The issue I see is
throughput for an iebgener step for instance even though it calls for
an input (and possibly an output tape) the step could last for 10
seconds or 30 minutes (or more) it would tie up that specific init
for that amount of elapsed time leaving the other jobs in that job
class waiting. It is in a way allocating resources (tape drives).
Ed
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