I believe that the net result of coding smaller blocksizes does result in
being able to store less data. If you had 1,000 volumes all defined as
3390-9s, and each volume had 100 datasets that filled the volume blocked at
512 bytes, you would store a fraction of the data if you blocked each of
those datasets at 1/2 track blocking. That is a function of the z/OS
archictecture.
I don't know exactly how the data is stored on the tracks, but I believe
that the result of smaller blocksizes means that you will store a lot less
data.
Ron Hawkins probably is the best definitive source on this subject.
Eric Bielefeld
Retired z/OS Systems Programmer
Milwaukee, Wisconsin
414-475-7434
----- Original Message -----
From: "Jantje." <[email protected]>
Newsgroups: bit.listserv.ibm-main
To: <[email protected]>
Sent: Tuesday, July 23, 2013 5:32 AM
Subject: Re: BLKSIZE=3120
Taking the risk of starting another flame war here...
Are there still any shops that have actual SLED? In today's world of
emulated DASD, would it really still hold true that using smaller block
sizes is actually wasting space? After all, these bytes are in the end
physically written to FBA devices with 512 byte sectors, no? In the old
days, there were inter-record gaps that took up space, but is this still the
case? And even if the emulation is so good that it simulates those, what is
happening with the actual capacity of the physical disks. Is that being
eaten by simulated IRG?
Thanks for shedding some light on this, whoever knows the internals of these
current DASD boxes,
Jantje.
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