Thanks for all this useful info. But, do not forget, collocation
processes will stay at a maximum of one at a time, this means only 2
drives will be needed and usefull for that.

Regards, Rene Lambelet, Nestle, VEVEY

> -----Original Message-----
> From: Wendrock, Richard O [SMTP:wendrro AT TEXACO DOT COM]
> Sent: Thursday, February 19, 1998 8:11 PM
> To:   ADSM-L AT VM.MARIST DOT EDU
> Subject:      Re: Planning for tape requirements for MVS
> 
> Good points Jerry and thanks... We are thinking about bringing in 4 or
> 5
> Magstar tape drives to improve collocation and reduce reclamation
> processing.  In that case we would not want to share those drives with
> other
> work... Thus the concern about the reasonable number to order...
> Regards,
> 
> 
> 
> > ----------
> > From:         Jerry Lawson[SMTP:jlawson AT THEHARTFORD DOT COM]
> > Sent:         Thursday, February 19, 1998 1:37 PM
> > To:   ADSM-L AT VM.MARIST DOT EDU
> > Subject:      Planning for tape requirements for MVS
> >
> > ---------------------------- Forwarded with Changes
> > ---------------------------
> > From: INTERNET.OWNERAD at SNADGATE
> > Date: 2/19/98 9:17AM
> > To: Jerry Lawson at ASUPO
> > *To: *ADSM-L at SNADGATE
> > Subject: Planning for tape requirements for MVS
> >
> ----------------------------------------------------------------------
> ----
> ----
> > -----
> > Interesting questions - I'll try to answer them as best I can.
> >
> > First of all, last year I had some issues with MVS tape allocation,
> and
> > ran a
> > short survey here.  One of the questions I asked was "do you
> dedicate tape
> > drives to ADSM on an MVS system.   The answer was a resounding "NO"
> - only
> > one
> > person (out of 25) did, and he was only doing it on one of his
> several
> > ADSM
> > systems.
> >
> > ADSM will use dynamic allocation to get a tape drive, and as such,
> when he
> > needs
> > one, will go to the head of the queue.  This is why most people let
> MVS
> > get the
> > drives and manage them for him.  I know at my shop, ADSM will use
> drives
> > in
> > bunches - a migration for example - we run 4 parallel tasks - so we
> would
> > need 4
> > drives.  I wouldn't want to dedicate 4 drives all of the time to
> ADSM.
> >
> > There is a priority among ADSM tasks - I don't remember what it is,
> but it
> > is
> > somewhat logical, as I recall - for example, a DB backup will
> preempt a
> > tape
> > reclaim, etc.
> >
> > Within ADSM, on the device level, you can control the number of tape
> > drives ADSM
> > will take - for example, If you don't want his use of drives to
> exceed 4
> > at one
> > time, you can set this limit, and then processes will wait until the
> > devices
> > become available.  Sort of lets you be politically correct.
> >
> > As far as when does he release a tape drive, there are a couple of
> answers
> > here
> > too.  First there is a mount retention period that you can set -
> this
> > allows
> > ADSM to hold a drive for a period of time after the task is finished
> with
> > a
> > tape.  The idea is that a lot of time the same tape will be needed
> again.
> > This
> > is most true in restores, where a customer might do a few files at a
> time.
> > If,
> > for example, you set mount retention at 5 minutes, and a user
> restores a
> > few
> > files, when the restore is finished, the tape will be held on the
> drive
> > for 5
> > minutes before it is released.  If the user wants some more files
> before
> > the 5
> > minutes, and they are on the same tape, the process will start again
> > immediately.  This is obviously of more value on a manual tape
> system,
> > than it
> > is on a robot driven system.
> >
> > The other answer to your question has to do with end of reel
> processing.
> > ADSM
> > does not follow a typical MVS paradigm here.  The intent of the
> design is
> > to
> > speed the process, and so at end of reel, rather than wait for a
> > rewind/unload
> > of the drive before a new mount on the same device, ADSM will ask
> for a
> > new
> > mount on a different device (assuming you aren't at the mount
> limit,) and
> > will
> > then issue the unload/rewind.   This works fine until MVS runs out
> of
> > drives,
> > and then the fun can start - ADSM will ask for a mount, he is under
> his
> > mount
> > limit, so he expects that they will be available, but they are not.
> MVS
> > will
> > put him at the top of the queue, but in the mean time, the old drive
> sits
> > and
> > waits - no unload is issued.  Depending on your system, this may or
> may
> > not
> > occur very often, just be aware.
> >
> > Hope this helps
> >
> > Jerry Lawson
> > jlawson AT thehartford DOT com
> >
> > ______________________________ Forward Header
> > __________________________________
> > Subject: Planning for tape requirements for MVS
> > Author:  INTERNET.OWNERAD at SNADGATE
> > Date:    2/19/98 9:17 AM
> >
> >
> > I am trying to determine how many tape drive we will need for ADSM
> on MVS.
> >
> > How does ADSM manage tape drives on MVS?
> >
> > Is there a priority amongst ADSM subtask?  Does a request for
> recover
> > carry
> > a higher priority over backup?
> >
> > When does ADSM release a tape drive? (at end of tape or end of task)
> >
> >
> > Regards,
> >