Yep. We ran into a 14-year old bug when trying to run one of our
products on a system it normally isn't run on. Eventually tracked it
down to an incorrect (CLC which should have been CLI) reference to a
PSA field which had always been zero. But on that one system,
someone had fired up IGVDGNPP and that field wasn't zero. Tilt.
Luckily we hit it before a customer (or IBM) did.
Good test tool. Why isn't it documented? The cat's out of the bag
now. Check with Google.
/Leonard
Jim Mulder wrote on 2/22/2022 11:37 AM:
Yes, the undocumented (but disclosed to ISVs) IGVDGNPP test tool will
modify all of the reserved fields in every CPU's PSA in order to expose
latent defects in code that happens to seem to work when reserved fields
contain zeroes. But since that may expose latent defects in other code
(IBM, ISV, or customer), it's not the kind of thing you would want to
use on a production system.
We of course use that tool on our test systems, so that we tend to
not have zeros at PSA+4 on our z/OS 2.5 test systems, which may
have contributed to the bug escaping our notice
until it got into the field.
Jim Mulder z/OS Diagnosis, Design, Development, Test IBM Corp.
Poughkeepsie NY
"IBM Mainframe Discussion List" <IBM-MAIN@LISTSERV.UA.EDU> wrote on
02/22/2022 10:26:40 AM:
From: "Charles Mills" <charl...@mcn.org>
To: IBM-MAIN@LISTSERV.UA.EDU
Date: 02/22/2022 02:28 PM
Subject: Re: 2.5 Heads Up
Sent by: "IBM Mainframe Discussion List" <IBM-MAIN@LISTSERV.UA.EDU>
Would using some "debug" type utility to store a non-zero value at
address 4
be a partial circumvention?
The pre-Z restart PSW is never used for anything now -- is that correct?
Charles
-----Original Message-----
From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On
Behalf Of Jim Mulder
Sent: Monday, February 21, 2022 10:03 PM
To: IBM-MAIN@LISTSERV.UA.EDU
Subject: Re: 2.5 Heads Up
Location 4 means address 4 (i.e. offset 4 in the PSA).
There was a latent bug from a prior release in the loop control
code so that it was erroneously fetching from address 4, and
behaving especially badly when the data at that location
is x'00000000', which it is as of z/OS 2.5. In prior releases,
it was x'000130E1' when in zArchitecture mode.
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