On 7/28/2023 5:04 AM, Larre Shiller wrote:
That said, you might want to check out IBM APAR OA61492 (and associated PE fixes). The
DASD UNMAP function (or the non-IBM DASD equivalent) seems to perform "the
same" Erase-On-Scratch function... but at the hardware level. We are using the EMC
equivalent and it is working seamlessly--no z/OS side overhead at all and practically
nothing at the DASD hardware level.
Dude! I can't believe I didn't know about this awesome new feature!!
Thanks for posting...
The only troubling part is this restriction:
* This support is available when all of *
* these conditions are met: *
* - data sets are on volumes not in copy * <---!!!
* services relationships * <---!!!
Our primary DASD volumes are in permanent incremental FlashCopy
relationships in order to reduce pressure on the DASD subsystem when
full-volume FlashCopy is needed for dumps, etc. I got the impression
after listening to a presentation from Glenn Wilcock at SHARE that this
was a best practice. Perhaps I misunderstood him or things have changes
since then, but either-way I'm starting to rethink that practice.
Another similarly-restricted function is the DSS SPACEREL command, which
we issue periodically on our SMS storage groups. Like this UNMAP
feature, it won't work with active copy services relationships. In that
case, we withdraw those relationships prior to running the SPACEREL
function. But that's something we do only a couple/few times a year so
it's not a big deal.
It sounds like EMC DASD doesn't have these restrictions? I'm betting
Hitachi doesn't either, but I don't know for sure...
I wonder what other IBM DASD clients are doing?
--
Phoenix Software International
Edward E. Jaffe
831 Parkview Drive North
El Segundo, CA 90245
https://www.phoenixsoftware.com/
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