Specifically, see
http://www.bitsavers.org/pdf/ibm/dasd/reference_summary/GX26-4577-0_3390_Reference_Summary_Jun89.pdf,
This reference Summary booklet contains on p10 the non-trivial
calculation formula for how many physical blocks will fit in a 3390
track, and also contains a chart on p18 showing the number of physical
blocks per track for all possible block sizes based on that formula. A
3390 CKD device requires allocation for Count and Key fields in addition
to the actual Data block, and space for gaps between fields and blocks.
Even though all 3390 devices these days are emulated on other physical
devices, the Operating System still thinks it is dealing with a 3390
device. The useful space on each track must be calculated by the rules
of 3390 architecture in order that all applications and access methods
sensitive to the DASD architecture will continue to work correctly.
Joel C. Ewing
On 10/25/21 09:44, Oscar wrote:
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?
Thanks!
--
Oscar
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Joel C. Ewing
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