In z/OS, for MVS, and SADMP IPLs, the support for pure z/Architecture IPL was introduced in z/OS 1.12. That is because I had time to work on it back then, and I was hoping that if it was implemented soon enough, we wouldn't need to roll it back to older releases via PTFs when some future z/Architecture-only machine got built. And that's how it worked out. The z14 was far enough in the future that no backporting to older release was needed.
That does not necessarily mean that z/OS 1.12 will work on on a z/14. It just means that the removal of ESA/390 isn't the thing that will make it fail. I don't remember which release introduced the DFDSS Standalone Restore support for z/Architecture-only machines. Jim Mulder z/OS Diagnosis, Design, Development, Test IBM Corp. Poughkeepsie NY "Timothy Sipples" <[email protected]> wrote on 01/09/2019 08:17:17 PM: > From: "Timothy Sipples" <[email protected]> > To: [email protected] > Date: 01/10/2019 12:58 AM > Subject: Re: z/OS 1.12 question > > To elaborate a bit on the possible technical reasons why z/OS 1.12 probably > won't work on an IBM z14 machine, even if you've applied every PTF you can > lay your hands on to z/OS 1.12, the z14 is the first machine model to drop > ESA/390 IPL support. As background, when IBM introduced z/Architecture > (64-bit) support in z/OS (all the way back when z/OS was born), the first > major step was to engineer z/OS so that it would still start the IPL > process in ESA/390 mode, as in OS/390, but then it would switch to > z/Architecture mode if available. Up through and including z/OS 1.5 the > operating system could run on either ESA/390 or z/Architecture machines. If > z/Architecture was available, it would switch into that mode automatically. > > IBM also offered some add-on software called the "z/OS Bimodal Migration > Accommodation" for those early releases of z/OS up through 1.5. That add-on > software would force z/OS to remain in ESA/390 mode on z/Architecture > machines. > > From z/OS 1.6, IBM dropped support for continuing the IPL and running z/OS > in ESA/390 mode. The z/OS-initiated switch early in the IPL to > z/Architecture mode became mandatory. z/OS 1.6 was the first z/OS release > that could only run on z/Architecture machines, and (after the early IPL > phase) it always ran in 64-bit mode. > > The z14 dropped support for ESA/390 IPL, so any operating system that > starts its IPL in ESA/390 (31-bit) mode doesn't work on that machine model, > with one caveat that I'll explain in a moment. As far as I know IBM only > backported pure z/Architecture IPL to z/OS 1.13 (under extended support) > and higher, not to z/OS 1.12 or prior. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
