On Sun, 22 Oct 2006 07:37:46 -0700, Edward Jaffe <[EMAIL PROTECTED]> wrote: > > Write-protected subpools?! No such thing! > Now that I think about it, I suppose that makes sense.
> I mentioned the CsvRentSp252 DIAG trap earlier in this thread.. What > I overlooked that. Several months ago, when you discussed this in ASSEMBLER-LIST, that keyword in Google found me a slide presentation (yours? IBM's? at Share?). It no longer appears. > that does is put RENT code into subpool 252, which is key zero storage. > Therefore, programs running in PSW key zero can modify SP 252 storage. > > To get complete protection of all RENT modules, you must use the > CsvRentProtect DIAG trap. That uses PGSER PROTECT to protect the modules > once they're loaded. I don't recommend that setting on systems older > than z/OS V1R8 because there are several popular IBM programs, residing > OK. Write-protected pages, not subpool. Is it likely that with evolution the behavior of those two options will become the default, and the list of exceptions will shrink? I suppose the transition will never be complete because of "dusty deck" concerns. Some non-IBM systems can mark segments as I-fetch only and D-fetch only. Does z/Series have this capability? It instantly traps on wild-branch-into-data. Might also provide a guideline for cache management. The recent discussion here and in links mentioned "very small" programs, which might load instructions and data into the same cache line. I assume this could happen even in a very large program, wherever instructions abut data. Would use of "DS 255C" be a good way to avoid the performance impact? Of course this could be ovecome by events if future hardware has a different cache line size. Will CSV and storage management ever allow load modules and data to occupy the same page? If so, a program might need to be protected with neutral zones on both ends. Does EX count as an I-fetch or a D-fetch? (Could even be model- dependent) -- gil -- StorageTek INFORMATION made POWERFUL ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
