In the case of multiple steps each allocating one file on the same tape,
and no AFF parameter used, there was (is?) a significant difference
between JES2 and JES3.
JES2 would allocate as many tapes as there were steps, and rewind an
unload the volume after each step and issue a mount for the same volume
on the next tape drive. JES3 had Tape High-Water Setup, and would
allocate a single tape unit for the volume, and not rewind and unload it
between steps.
The only fix for JES2 was to add UNIT=AFF and DISP=(,PASS) to the JCL.
JES3 didn't mind that you left them out.
I can't test this as I have no JES3 system.
Tom Russell
On 2013-09-01 12:00 AM, IBM-MAIN automatic digest system wrote:
Date: Sat, 31 Aug 2013 02:19:26 -0400
From: Gerhard Postpischil<[email protected]>
Subject: Re: UNIT=SEP still alive (?)
On 8/30/2013 9:22 PM, Robert A. Rosenberg wrote:
>I know for multi-volume datasets UNIT=(TAPE,2) handled the mount of
>volume3 while volume1 rewound and unloaded. I do not remember if you
>could allocate 2 units and have concatenated input volumes alternate
>between them. AVR might have helped since it say "Find the device with
>the Tape Volume and allocate the DD to it" but I do not think it would
>handle the case where you want to reuse a drive where the tape has
>unloaded - It was for allocation at step start.
All true, but the thread is about distinct DD cards, beginning with SEP,
and drifting into AFF. Joel Ewing complained that the default takes too
many drives, but hasn't offered a practical means for IBM to allocate
drives, when the user specifies neither SEP nor AFF, that would allow
reducing the allocation to less than one drive per DD.
Gerhard Postpischil
Bradford, Vermont
--
Tom Russell
“Stay calm. Be brave. Wait for the signs.” — Jasper FriendlyBear
“... and remember to leave good news alone.” — Gracie HeavyHand
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