W dniu 25.10.2021 o 16:44, Oscar pisze:
Hi there,
There's something I'm being missing, but acording to my numbers, there
should be 13, not 12:
Bytes per track: 56,664 bytes
Bytes accessible per track: 55,996 bytes
CI size: 4096
Physical record size: 4096 bytes
Physical records per track (Bytes accessible per track / physical
record size): 55,996 / 4096 = 13.6708984375 = 13????
What I'm missing?
You're missing CKD deep details.
Instead of looking for old documentation just do some quick test:
allocate single-track datasets. Each of them can be VSAM or just PS, it
doesn't matter. However for PS it would be a little bit easier.
Important: specify RECFM=F and LRECL=BLKSIZE=n, where n is any number
you want to test. I would suggest the following:
n=10
n=512
n=4096
Then use your ISPF editor to fill the datasets with some data. You will
find out how many records/blocks fit on a track.
Note: you won't get more than 86 blocks per track. Even very short ones.
Reason? Gaps between blocks. More specifically: you block (physical
records) consist of C and D. CKD is for Count Key Data. Your PS file has
no K, so it is just C D. And gaps between them. And R0 which is also
some physical record. And HA - Home Address, another 5-byte physical
record. And 3390 is FBA under cover, with cell size=34B. And all the
gaps or physical records (including C as separate entity) occupy one or
more cells, not fraction.
BTW: The above is part of "extra material" which I sometimes teach
during VSAM course.
--
Radoslaw Skorupka
Lodz, Poland
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