The following message is a courtesy copy of an article
that has been posted to bit.listserv.ibm-main,alt.folklore.computers as well.

"Charlie Gibbs" <cgi...@kltpzyxm.invalid> writes:
> On the other hand, if you wrote 200-byte physical records on a
> CKD device, the overhead (inter-record gaps, count fields, etc.)
> would exceed 50%.

re:
http://www.garlic.com/~lynn/2010d.html#0 PDS vs. PDSE
http://www.garlic.com/~lynn/2010d.html#9 PDS vs. PDSE

DASD capacity forumulae ... from my conversion of gcard ios3720
http://www.garlic.com/~lynn/gcard.html#26.3

DASD Capacity Formulae

Device  Cyls   Tracks   Track           Bytes per record
type    /pack   /cyl   capacity    without key        with key
2305-1     48     8      14568      432+D              634+K+D
2305-2     96     8      14858      198+D              289+K+D
2314      200    20       7294      101+(D)534/512     146+(K+D)534/512
                                   D (last on track)  45+K+D (last on track)
3330-1    404    19      13165      135+D              191+K+D
3330-11   808    19      13165      135+D              191+K+D
3340-35   348    12       8535      167+D              242+K+D
3340-70   696    12       8535      167+D              242+K+D
3350      555    30      19254      185+D              267+K+D
3375      959    12      36000      224+#(D+191)       224+#(K+191)+#(D+191)
Device  Cyls   Tracks   Track           Bytes per record

... snip ...

3375 is a physical 3370 FBA (512byte blocks) with CKD emulated on top.
All current CKD devices are actually physically fixed-block with CKD
emulated on top (and things are quite a bit more complex)

-- 
42yrs virtualization experience (since Jan68), online at home since Mar1970

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