You are further illustrating my point. Your astonishment was due to your inexperience.
The use of REFR for storage error recovery was only in predecessors of MVS, and that was before my time at IBM. I only know about that because of Shmuel's posts about it. Although it was before my time, I would guess that the key 0 protection for RENT programs from APF authorized libraries was added only because it was required for system integrity, and limited to APF authorized libraries in order to avoid migration impediments that would have resulted from breakage to existing self-modifying RENT programs in non-APF authorized libraries. That would have been consistent with MVS's emphasis on compatibility, and thus is not astonishing to me. Your "by happenstance it is refreshed and fails" scenario is unlikely to ever occur, since refreshing is currently done only for LPA modules, which are DAT-protected. z/OS will not be implementing refreshing for storage machine checks. The probability of a storage machine check on current machines is so low that, if anything, we would be simplifying or removing storage error machine check processing in z/OS, not enhancing it. In fact, while doing some work on System Trace in z/OS 2.5, I discovered that exploitation of 1MB frames for trace buffers in z/OS 1.10 had introduced a bug where a storage error machine check recovery for trace structures could result in an infinite loop. Based on discussion with hardware engineers about the projections for storage machine checks on the machines supported by z/OS 2.5, I remediated that by simplifying the recovery to just discard and rebuild the whole trace structure for a processor instead of trying to fix the old logic for removing a single 4K frame from the processor's trace structure. Jim Mulder z/OS Diagnosis, Design, Development, Test IBM Corp. Poughkeepsie NY "IBM Mainframe Discussion List" <[email protected]> wrote on 09/01/2021 01:58:03 PM: > From: "Paul Gilmartin" <[email protected]> > To: [email protected] > Date: 09/01/2021 02:40 PM > Subject: Re: RENT binder option > Sent by: "IBM Mainframe Discussion List" <[email protected]> > > On Wed, 1 Sep 2021 13:25:03 -0400, Jim Mulder wrote: > > ... > > As to the Astonishment in POLA, I would > >suggest that astonishment is relative to the > >experience of the beholder, ... > > > The oldest memories are the sharpest. I remember vividly my > astonishment as an MVS/370 novice when I discovered that > RER programs were not protected against modifying themselves > despite ready availability of hardware facilities. (Then I could > grasp the PoOps; no longer.) > > I was even further astonished to learn that a program need to > be Authorized in order to not modify itself. > > I imagine a program incorrectly marked REFR which depends > on self-modification. It works for years until by happenstance > it is refreshed and fails. Of course: "User Error. WAD." > > --gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
