Edward Jaffe wrote:
John Eells wrote:
Paul Gilmartin wrote:
<snip>
I.e. 32760. So I can equally well use BLKSIZE=0 for load module
libraries as for
other data sets. It matters little to me whether BLKSIZE gets set by
SDB or by
the binder.
<snip>
It gets set by the first program to open the data set. If that's
always the Binder, it appears from your test that you get 32760.
Right. The only accurate SDB test occurs when using IEFBR14. Otherwise,
results may vary depending on which program opens the file.
It's been a Long Time since we did the research into all this
that led to changes in IBM's internal packaging rules and what
happens in ServerPac JCL, but as I recall...somewhat hazily at
this point...
Since IEFBR14 doesn't issue OPEN, I think the block size for an
SDB RECFM=U data set that happens to be allocated to it remains
indeterminate (perhaps set to zero in the F1DSCB), and won't
change until a program that *does* issue OPEN against the data
set has been run.
I can't recall for certain (and I don't have time to test it) but
I seem to recall that IEBCOPY might use the input block size to
set the output block size in this case. Paul's test with the
Binder seems to show that it will set 32760, but unless
everything is bound to load the data sets (including DLIBs), this
does not cover all possible cases.
Since ServerPac loads data sets using IEBCOPY COPYMOD, setting
the block size to 32760 explicitly when the data sets are defined
causes IEBCOPY honor their block size, which always minimizes
the space required for load modules (which in turn has some
downstream potential performance benefit for Fetch processing
depending on frequency of use, cache hit ratios, the phase of the
moon, and so on).
I'd suggest the same for anyone loading system software with
IEBCOPY: Use COPYMOD and a block size of 32760.
So far as I know nobody has done much to look at the potential
benefits and downsides of using 32760 for application load
libraries, so this recommendation extends only to system software
at the moment.
--
John Eells
z/OS Technical Marketing
IBM Poughkeepsie
[EMAIL PROTECTED]
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