Dennis Trojak wrote:
How many cylinders on a 3390-27? I see conflicting doc of 32760 cyls or 3*10017 which is 30051. Can anybody confirm? Dennis
The "non-real" designations for 3390-nn are simply labels used to simplify conceptual management of volume sizes. A number of other intermediate volume sizes can also be defined and used.
Given that there is no such thing as a "real" 3390-27, in my opinion you can make equally valid (or otherwise) arguments for the number of cylinders in a 3390-27 being:
- 30051 cylinders, 9X the size of a real 3390-3 (which has 3339 cylinders) or 3X the size of a real 3390-9 (which has 10017).
- 31767 cylinders, a bit over 27,000,000,000 bytes of total device capacity (depending on block size, etc.).
- 32760 cylinders, half the *implementation* limit for non-EAV ECKD DASD (the implementation limit is 65,520 cylinder), and half the size of a "3390-54" (for which there is also no "real" device).
- 32768 cylinders, half the *architectural* limit for non-EAV ECKD addressing (if you don't count the reserved cylinders from 65521-65536 in the implementation).
- 34109 cylinders, a bit over 27 GiB of total device capacity (again depending on block size, etc.).
I would expect the two most common answers to be the ones you asked about; that is, some will want their "3390-27" devices to be 3X the size of their 3390-9 (or "3390-9") devices, and some will want their "3390-27" devices to be half the non-EAV maximum volume size. It all depends on whether you're looking from the maximum down or the minimum up.
Because everything is emulated these days, making all the designations whatever is most convenient for the person doing the designating at the moment, the most important question simply *has* to be: Why are you asking?
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