On Thu, 1 Jul 2010 09:18:46 -0500, John Hooper <[email protected]> wrote:
>Fifteen years ago I wrote a facility that front-ends the ENQ SVC. It traps all
>ENQ requests and if SYSDSN ENQ comes back with a return code of 4 it
>examines the environment, issues console messages, and usually waits a
>minute and tries ENQ again. Thus a test job reading a production file would
>not cause a production job to fail but would keep trying and give the console
>operator a chance to cancel the test job or wait for it to finish.
>
>This facility is designed especially to eliminate the following messages:
>
>IKJ56225I DATA SET MYTEST.TEST.ENQ.FILE ALREADY IN USE, TRY LATER
>IKJ56225I DATA SET IS ALLOCATED TO ANOTHER JOB OR USER
>
>Anyway, it works fine under z/OS 1.9 but doesnt work under z/OS 1.11.
This actually was changed in z/OS 1.10, so it wouldn't work on that OS
either. This change also broke some tools like the popular "BYPASSNQ" from
Gilbert St. Flour (CBT File 183).
Here is a note that I have from an IBMer with more detail:
"In z/OS R10, the Allocation component changed to use LINKAGE=SYSTEM
for all ENQs to provide better performance and efficiency. Some of
those ENQs were changed back to LINKAGE=SVC via APAR OA29286, however
SYSDSN ENQ was not. Moreover, there are no plans to change the
SYSDSN ENQ back to LINKAGE=SVC. (Also, we may choose to revert those
changed linkages in OA29286 back to LINKAGE=SYSTEM in a future
release.)"
"Programs that rely upon SVC screening for finding and changing ENQs
should be using GRS exits <some text deleted> For information on GRS
exits, see the MVS Installation Exits documentation. Relying upon
SVCs for ENQs is not supported and would be exposed to this type of
internal change if and when it occurred."
Mark
--
Mark Zelden - Zelden Consulting Services - z/OS, OS/390 and MVS
mailto:[email protected]
Mark's MVS Utilities: http://home.flash.net/~mzelden/mvsutil.html
Systems Programming expert at http://expertanswercenter.techtarget.com/
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