Not Your Dad's Mainframe: Little Iron 3999
On Mon, 10 Jul 06 10:01:25 GMT in alt.folklore.computers,
Between PER and regular halt-examine-deposit facilities, you effectively had DDT built into the kernel.
Used it seriously a couple of times: to check against the source for the cause of a bug, and to check that our local fix worked, before reporting officially as an APAR (Authorised Program Analysis Report aka SPR) with suggested patch: of course, the eventual officially released PTF (Program Temporary Fix) looked nothing like my patch; and to find out why a newly installed version of a DB product didn't come up: a dynamic library was missing in the startup script, and the DB wasn't checking the results from calls to routines to see if they were present.
Anne & Lynn Wheeler for a little ios3270 drift, an ios3270 version of the green card was done; here is a crude conversion from ios3270 to...
To debug the OS code, you ran the test instance under the prod instance and used the prod facilities to debug the test OS (which could be another copy of prod on an alternate system pack), under a virtual machine config which matched the real machine config, but had only the necessary subset of resources allocated.
It was SOP to build updated OS versions on the alternate system pack, IPL (aka boot) it under the test virtual machine config, and test as much as feasible, before booting the alternate system pack standalone on the real machine and testing everything was okay.
-- Thanks. Take care, Brian Inglis Calgary, Alberta, Canada
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Not Your Dad's Mainframe: Little Iron 4000
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