Storage keys were available all the way back to OS/360.
-- Shmuel (Seymour J.) Metz http://mason.gmu.edu/~smetz3 ________________________________________ From: IBM Mainframe Discussion List <IBM-MAIN@listserv.ua.edu> on behalf of Peter Relson <rel...@us.ibm.com> Sent: Sunday, July 15, 2018 8:54 PM To: IBM-MAIN@listserv.ua.edu Subject: Re: Linklist and APF <snip> There's also REFRPROT nowadays. But that should have never been needed as an option; it should have been the universal behaior ab ovo. How much extra would it have cost to load user programs as well as system programs into write-protected storage? </snip> Page protection did not exist at the time that this logic was introduced. So "ab ovo" was not possible if used the way I interpret it. Changing the behavior when page protection was added would be viewed, properly, as incompatible and thus unacceptable. And the extra storage utilization (page multiple on page boundary) might have been felt to be unacceptable too (perhaps no longer). Users are creative and might have chosen to rely on the existing documented behavior. It is also well known that the system does not "protect" against reentrant programs writing into themselves, just makes it harder. And it is also well known that a program could write into itself and still be reentrant (although that is surely frowned upon these days). Peter Relson z/OS Core Technology Design ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
