Peter, My understanding for what Jim said is a little different.
Actually Jim wrote something about DREF three years ago and I happened to find it in the archive: --------------------------------------------------------------------------------------------------- There are some important differences between *DREF* and fixed storage even when there is no expanded storage. 1. *DREF* storage does not get backed until it is referenced (other than the first page of the Getmain request). 2. The real storage address backing a *DREF* page can be changed at the whim of RSM. The real address backing a fixed page can only be changed by swap processing (and thus cannot change while you are non-swappable, or holding serialialization which prevents you from being swapped (like your local lock or by being disabled). ------------------------------------------------------------------------------------------------------------- So my understanding is: After your first reference to a DREF page, the frame *can be copied to ESTOR if you have that stuff. Even if we don't have ESTOR, something still can be done by RSM for DREF frame which is impossible for FIXED frame. That is, RSM can directly copy the DREF frame to another frame. So the real address for a DREF page can change even without ESTOR and swapping out. On 10/9/07, Hunkeler Peter (KIUK 3) <[EMAIL PROTECTED]> wrote: > > Keep in mind that MVS is permitted to move a unfixed backed DREF > >page to another real frame, so do not assume that the real address > >of an unfixed backed DREF page will not change. > > ...which makes DREF storage behave more like pageable storage than > fixed (like xxSQA): It is not backed until referenced, it can be > paged out (when there is ESTOR, so not on z/OS). > > -- > Peter Hunkeler > Credit Suisse > > -- Best Regards, Johnny Luo ---------------------------------------------------------------------- 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
