check the iocp manual - it's the CSS-ID (the logical channel subsystem id).
http://www-01.ibm.com/support/docview.wss?uid=isg2de3388ad7e19bffc85257768003f170e&aid=1 page 68 and of course page "303", which says the 2817 has max of 3 for css-id, and a max of 2 for subchanel set id. p.s. i loved the history lessons, most of them being fairy tales. and dark distant foggy memories. The truth though is more fascinating . it's sad people can't let go.... device addressing was 3 digits(hex) . let it go... it's all now chanell-sets and iodf device numbers. the old days are gone, and should be forgotten. let it go, ok? A few yerars back IBM was well aware of the "device number running out"problem, they addressed in a few ways, 1) more "data" per the "addressed-device" - notably the dasd devices. 2) add channel sets and 3) add virtual "layering". The thought was that this would allow the HCD/IOCP/HSA areas to be managed better(controlled). and circumvent the "software intrusion into created 3or4-byte addressing" i.e. 5 hex digites need 3 bytes to live in. and 3 bytes would upset the world of ZOS, (JCL,control blocks, etc etc). Imagine the 2 byte fields "abcd" (that reresented 4 digits in 2 bytes) expanding to larger size as well. it was a nightmare, to change pgms that dated back years and decades to "evaluate and change", let alone user-pgms sysprogs wrote. a lot of money here. best solution- keep 4 char device numbers asis, add a new plane of existance and let the hotshot sysprogs deal with it. first confusion, then awareness (i.e. read newera software share presentation handout --session 10471 last march titled "IODF, etc.", and/or other share sessions in last 20th century hosted by IBMers in a freeforall on this topic, it's been over a decade -- where were you?) so, it was decided to go another route instead - the one they implemented starts at the IOCP level, and will one day be "better known". ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
