Subject: Re: How to precisely calculate the number of bytes per track for a
From: Bo (g.goersch@worldnet.att.net)
Date: Fri Aug 19 2011 - 09:23:06 EDT
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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