RE: How to precisely calculate the number of bytes per track for a

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Subject: RE: How to precisely calculate the number of bytes per track for a
From: Kevin Corkery (kcorkery@live.com)
Date: Fri Aug 19 2011 - 09:51:59 EDT 

Maybe this may be of help ...

http://publibz.boulder.ibm.com/cgi-bin/bookmgr_OS390/BOOKS/am3u1001/B.1.2

http://publibz.boulder.ibm.com/cgi-bin/bookmgr/BOOKS/IESVGE60/7.4.3?SHELF=IE
SVSE80&DT=20100803123026#TBLCISDATC

The first is the 3390 track capacity chart for sequential files and the
second is the VSAM capacity (based on CISZ) for various ECKD devices.

-----Original Message-----
From: owner-vse-l@Lehigh.EDU [mailto:owner-vse-l@Lehigh.EDU] On Behalf Of
Beggs, Beth A.
Sent: Friday, August 19, 2011 9:29 AM
To: VSE Discussion List
Subject: RE: How to precisely calculate the number of bytes per track for a

Yes, those multiple posts were a combination of user and system error! I
just removed the dups.

Your answer does help.  In addition to straight VSAM space, we use EPIC disk
which is offloaded to (virtual 3490) tape. We do not have any tape blocksize
in excess of 32767. Is that also an obsolete limitation?

-----Original Message-----
From: owner-vse-l@Lehigh.EDU [mailto:owner-vse-l@Lehigh.EDU] On Behalf Of Bo
Sent: Friday, August 19, 2011 9:23 AM
To: VSE Discussion List
Subject: Re: How to precisely calculate the number of bytes per track for a

Beth;
I have noticed that you have opened a number of topics with this same
question, I am presuming you are anxious for an answer.

The capacity of a 3390 track is a constant, "Every 3390 disk volume contains
56,664 bytes per track, 15 tracks per cylinder and 849,960 Bytes per
Cylinder."  The CISIZE or BlockSize is the variable which determines how
much data you can store on a device.


In the old days a Blocksize was limited to 32K, if you had the "maximum"
block size of 32,0000+ bytes you could write one block per track, this made
the other 24,000 bytes useless and you wasted 2/3 of each track.  To utilize
a dasd device to it's fullest you should use a blocksize or CISIZE that
allows for the maximum records per track.  If your CISIZE is the 23,552 or
45,056 you indicated you will still lose around 10k per track.  I like to
use 18000 as a guideline, gets me 3 blocks per track with a minimum of
waste.

Hope that helps.

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