Blaicher, Chris wrote:
The limit for CKD volumes is a little more than 54GB. I come up with a
number closer to 500GB. Past that and IBM will need to go to logical
volumes on a physical volume. The reason is the CCHHR count field.
Max CC is FFFF, which give 65536 cylinders (don't forget cylinder 0)
Max HH is E, which gives 15 tracks per cylinder
That gives:
65536 cylinders times 15 tracks times 56664 bytes = 983040 tracks *
56664
983040 tracks * 56664 = 557,053,378,560
Max CC I agree is FFFF. That's obvious. But, max HH = E? My hex
calculator disagrees. This is not a CKD restriction. It is a
self-imposed restriction by those not wishing to change the trk/cyl
constant. I guess you're one of them.
Remember, 3350s had 30 trk/cyl. Since there are no SLEDs any more,
there's no reason we cant have HH = 7FFF or even HH = FFFF except for
the 3390 geometry compatibility issue. And, nothing says we can't make
bytes/track larger either.
Even if 15 trk/cyl must be retained, then why not steal the four
"wasted" bits from the HH and use it to extend CC?
It seems to me that there are several practical alternatives...
--
Edward E Jaffe
Phoenix Software International, Inc
5200 W Century Blvd, Suite 800
Los Angeles, CA 90045
310-338-0400 x318
[EMAIL PROTECTED]
http://www.phoenixsoftware.com/
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