For normal volumes, CCHHR where each letter is 8 bits. For EAV volumes this is defined to x'ccccCCChrr'' where each letter is 4 bits. rr = x'00'- x'FF' H 'x'0' - x'e' (since 3390s have 15 heads). CCCcccc is the cylinder number, with CCC=x'000' (non-eav 1 to 64K cylinders 56GB) to 00F (800GB EAV) and the cccc is x'0000' - x'ffff'' 0 to 64K tracks
On Mon, Aug 25, 2025 at 7:44 PM Paul Edwards < [email protected]> wrote: > I am interested in the "artificial device" described on page 330 here: > > https://publib.boulder.ibm.com/epubs/pdf/dgt2u140.pdf > > (for use by iebcopy). > > I am actually interested in PDSes, not PDSE, but I would > expect that an artificial device is the same either way, and > that I could use it for a PDS too. > > It is defined as: > > 65536 cylinders > 256 tracks (heads) > and the tracks are 16M bytes, which means that regardless > of the blocksize, you can fit 255 records in it. > > According to that page, it is subject to limits described here: > > https://www.ibm.com/docs/en/SSLTBW_3.1.0/pdf/idad400_v3r1.pdf > > But I'm not sure which page is relevant. > > I see limits on page number 41, but that's 16 MB for a single disk. > > This artificial machine can do that in a single track! > > What I'm interested in is why the number of heads is limited to 256. > > I normally see CCHHR - so that should mean 65536 heads, the > same limit as the cylinders. > > Any idea why the heads on an artificial machine are only 256, > and whether that is documented as suggested by page 330 > of the first manual? > > Thanks. Paul. > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN > -- Mike A Schwab, Springfield IL USA Where do Forest Rangers go to get away from it all? ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
