Barry Merrill wrote:
Educate me why 32k with wasted space on a track is better than half track;
I do defer to your knowledge and do not argue you are not right, but why?
Basically, it's because RECFM=U does not behave like fixed blocks.
The block size of a load library sets the maximum length of a text
record. As Paul points out, the Binder uses TRKBAL to determine the
space left on a track. IEBCOPY COPYMOD (not COPY) does the same. Both
write short blocks when needed to maximize space utilization on every
track. Block sizes below the maximum can only cause more text (and
control) records to be written, to the detriment of space allocation and
(sometimes) performance.
Anyone can try this out: Copy LINKLIB using COPYMOD to different data
sets with different block sizes and see what happens. You might find a
block size past which things stop getting better, but you won't find a
larger one that makes it worse.
Search the archives for prior discussions on this with my name attached
for far more detail.
--
John Eells
z/OS Technical Marketing
IBM Poughkeepsie
[email protected]
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