On 3 November 2017 at 14:20, John McKown <[email protected]> wrote:
> On Fri, Nov 3, 2017 at 12:50 PM, Phil Smith <[email protected]> wrote: > > > I'm trying to understand more about using a SUBSYS= on a DD. The problem > > is that Googling "z/OS" and "subsys" or "subsystem" isn't exactly > fruitful, > > and the IBM-MAIN archives search seems to be broken (unless nobody has > ever > > mentioned "jcl"). > > > > Can someone point me at a book that talks about what this does and how > one > > would implement one? > > > > Example is File 290 on the CBT. Go here: http://cbttape.org/cbtdowns.htm > GPSAM (file 290) is indeed remarkable in that it's 40 years old, and the code and doc are still 99% valid on current z/OS. To say nothing of the high quality of Howard Gilbert's short but to the point doc. It's entirely possible that GPSAM may already provide the infrastructure for what you want to do, though much of its initialization would be done differently if written today. Read more here: > > https://www.ibm.com/support/knowledgecenter/en/SSLTBW_2.1.0/ > com.ibm.zos.v2r1.ieaf200/ssiint.htm > A lot has changed in 40 years. Thing is, the complete subsystem interface has never been fully documented. GPSAM was written at a time when the MVS source code was the definitive documentation, and it was quite possible, as Howard Gilbert did, to figure out how things *really* worked in the subsystem world. The current subsystem doc completely fails to mention more than half the standard subsystem calls at all, and of course the source code is generally no longer available, so it's become an opaque BLOB. :-( And of course a lot of nifty new function and services have been added to and in support of the SSI. The only good part to the story is that JES2, which implements a good number of the undocumented subsystem calls, including most of those related to DD SUBSYS=, is still mostly not OCO. Assuming you have z/OS access, looking at the JES2 source for allocation and open/close/put/get can be very instructive. Tony H. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
