MIDAW and Dynamic Activation

[Lizette Koehler]

I have a strange problem going on right now.

We are in the process of upgrading our EMC dasd from DMX3000 to DMX4500.  We
have just recently got the DMX4500 connect but not setup to be used.

For some reason we are having MIDAW activated on our systems that can
support MIDAW.  I did not issue a SETIOS MIDAW=YES so I am not sure how it
is getting turned on.

So I issue the SETIOS MIDAW=NO, it says it is disabled.

However when one specific Syncsort Job runs, the Output shows that MIDAW was
used even though the D IOS,MIDAW shows disabled

Has anyone seen that?

Lizette

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[Mark Jacobs]

It wouldn't surprise me if Syncsort turns on MIDAW for its I/Oif the
processor supports it regardless of the IOS setting.

--
Mark Jacobs
Time Customer Service
Tampa, FL
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[Knutson, Sam]

The IBM default for MIDAW is enabled. Did you updated PARMLIB?

For IECIOSxx.

MIDAW:

Use the MIDAW statement to enable or disable the MIDAW facility on a
system. If no MIDAW statement is specified, the MIDAW facility will be
enabled on the system by default.

Subtopics
Parameters for MIDAW


Parameters for MIDAW:

MIDAW=YES|NO
Specifies whether the MIDAW facility is enabled or disabled on a
system.

Default: YES

I feel this is reasonable now. I objected when MIDAW support was
introduced and it defaulted to YES as we were a site that hit some
APARable problems related to MIDAW.

If you want MIDAW turned off at IPL updated IECIOS00 to reflect MIDAW=NO

I am currently using MIDAW and HYPERPAV without any problems.

BROWSE SYS1.PARMLIB(IECIOS00)
Command ===>
MIDAW=YES
HYPERPAV=YES

I believe that SyncSort constructs it's channel programs according to
what IOS dictates is the currently allowed road rules and handles MIDAW
enablement being changed dynamically. I don't know how they could do
otherwise. IOS and the hardware are in charge here they just submit a
channel program and if MIDAW is disabled it won't work.

We are also running SyncSort 1.3 with good results.

We have primarily IBM DASD 2107 and 2105.

Best Regards,

Sam Knutson, GEICO
System z Performance and Availability Management
mailto:sknu...@geico.com
(office) 301.986.3574

"Think big, act bold, start simple, grow fast..."

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[Reda, John]

Lizette,

There are a number of checks that are done before the sort attempts to use MIDAW. The final check is when we look at the UCBMIDAW bit in the UCB involved. If a channel program tried to use MIDAW and it was disabled on the system level, IOS would fail the channel program with a PGM CHECK. I have seen this situation. It is possible that the sort is really not using MIDAW and the message is being posted in error. We have never seen this and however unlikely, it is possible. If you would contact me off-list, we can discuss what the next steps could be.

John Reda
Syncsort, Inc.
201-930-8260

[, IBM Mainframe Discussion List]

In a message dated 7/29/2008 6:55:10 A.M. Central Daylight Time,

jr...@SYNCSORT.COM writes:
>The final check is when we look at the UCBMIDAW bit in the UCB involved.
If a channel program tried to use MIDAW and it was disabled on the system
level, IOS would fail the channel program with a PGM CHECK.

I look at that same UCB bit and nowhere else. I trust the rest of the
operating system to turn the bit on if the processor, controller, device, and
parmlib settings all allow it. So far I haven't gotten any channel program
checks, which by the way are detected by the Channel Subsystem (part of the
processor hardware microcode) rather than IOS (software component of the operating
system).

Bill Fairchild
Rocket Software

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