You might consider SMS compression to reduce the physical size of the
file. If you do, change the BLKSIZE to 32760 as SMS compression
writes full tracks and the BLKSIZE becomes logical (the size of the
buffer used in passing date to/from the application).
Michael
At 11:44 AM 2/21/2024, Bob Bridges wrote:
I'm not a sysprog (just a security geek), but I can at least
allocate datasets, and at the start of this year it fell to me to
allocate a new dataset in which are logged all changes made in the
security system. Past year's log are in the 12000-track range, so I
started with a smaller allocation while I took the time to talk to
our sysprog about space requirements. It's populated from a daily
production job, by the way.
When I re-allocated it, on his advice I tried a multi-volume and
extended allocation (PS-E). Almost immediately the job started
bombing, claiming that the first four volumes it tried didn't have
the necessary space to add an extension. The sysprog is puzzled -
says it should have looked in volumes that DO have the space, not
the ones that don't.
Second attempt (I don't count the temporary smaller allocation) I
kept PS-E but dropped the multi-volume requirement. I've never done
one of those anyway, and don't trust 'em. The system promptly
dropped the extra tracks I allocated, and a day or two later the job
started bombing with a B37-04.
Third attempt: Forget PS-E (I'm unfamiliar with that too) and just
used SPACE=(TRK,(9000,1000)). That seemed to work for a whole week,
but I just noticed that something, somewhere, has released extra
space AGAIN; 3.4 tells me it's now 1960 tracks and 83%. The job
isn't bombing yet; some time later in the year I'm guessing it's going to.
Pardon my frustration: WHAT THE HECK IS GOING ON? Why does it keep
releasing space although I never specified RLSE? The sysprog
doesn't know either - but he's an external contractor who just took
over the system a few months ago and if it's something simple he may
not be aware yet of ... I dunno, something in SMS maybe?
Some wrinkles that may or may not be relevant:
1) The dataset is written using a REXX exec that calculates the DSN
by reference to the current year. This relieves folks from having
to update the JCL every year, but maybe something about the way the
exec does the allocate is causing the problem? I'm guessing not,
because as far as I now this job has run correctly for years. But
just in case:
"ALLOC DDN(CHG$$OT) DSN('<dsn>') MOD CATALOG REUSE",
"SPACE(300,30) CYLINDERS RECFM(V,B) LRECL(304) BLKSIZE(27998)"
2) I don't know anything about SMS, but could something there be
releasing space?
3) What IS extended PS, anyway? I'm told it allows more than 16
extents, but a) how many more? And b) how else is it different?
4) I allocated the dataset each time using not batch JCL but 3.2 ...
expecting there's no difference.
---
Bob Bridges, robhbrid...@gmail.com, cell 336 382-7313
/* Law #6 of combat operations: If it's stupid but it works, it
isn't stupid. */
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