Harold Grovesteen wrote:
Have we actually determined WHY these protection exceptions
are occurring, albeit apparently legitimately with VM/370?
If so I missed understanding that. Yes, I got that CS is
being used to test writability to a location. But WHY is
VM doing THAT? This is the part I missed.
It's not VM that's doing it: it's MVS (i.e. the VM guest).
CS is an unprivileged instruction, so when MVS executes it, it causes a program check (which Hercules then logs).
Does it make sense to add protection exceptions to the VM
OSTAILOR setting rather than setting it manually?
No. Because Protection Exceptions should NOT normally be occurring. It's not an exception that is considered "routine" (expected) in a normal operating environment (which are the only type of exceptions that OSTAILOR is designed to filter).
One would expect that if this is a "normal" situation with VM/370
MVS. (Not VM)
that the VM setting
MVS setting. :)
would turn this report off.
Correct! Which is precisely WHY it's *not* turned off! Because it's NOT considered "normal/expected"! It's *unusual*. It's not something that regularly (routinely) happens in a normally functioning operating system.
(Obviously it is reported when OSTAILOR is not being
used.)
Or even when OSTAILOR *is* used, which was what I tried to make clear. That's why if MVS 3.8j is being run either natively -OR- under VM, you (currently!) need to add a "PGMTRACE -04" statement to your Hercules configuration file if you want to suppress their being reported by Hercules.
What mystifies me is why after years of people using VM/370
and MVS as guest that this is the first time this apparently
legitimate situation has arisen.
Actually it's not the first time. As Dave pointed out in his reply it was actually mentioned over 19 years ago too:
(I get it that obviously without OSTAILOR the report would happen.)
But why protection exceptions IN THIS CASE must be manually
turned off is what confuses me.
Because Hercules does not consider such exceptions to be "routine" (ordinary/expected) in a *normally* (properly!) functioning operating system! Hercules considers such exceptions to be "unusual" and "out of the ordinary" and usually indicative of a programming error. Thus, by default, it does NOT filter them out and reports them instead.
(This sort of gets back to why VM/370
MVS!
is testing location writability.) That would still suggest
that there is something unique going on here that others have
not encountered. Or maybe they were all smart enough to know
to manually turn off reporting of protection exceptions.
I think the thing that is unique that is going on here is the distributers/maintainers of the MVS 3.8j and VM systems ship their product with OSTAILOR QUIET purposely enabled in order to prevent this very issue. It only popped up this time because Jim Snellen reported seeing the messages in his log file because he obviously WASN'T using the stock Hercules configuration file that comes shipped with the normal MVS/VM distributions, and was instead using a Hercules configuration file that he constructed himself (probably via my HercGUI, which specifically mentions using NULL or QUIET is *not* recommended).
--
"Fish" (David B. Trout)
Software Development Laboratories
mail: fish@...
