I think the term "pointer compression" is relevant here - to java heap just above 2GB.
Cheers, Martin Martin Packer, zChampion, Principal Systems Investigator, Worldwide Banking Center of Excellence, IBM +44-7802-245-584 email: martin_pac...@uk.ibm.com Twitter / Facebook IDs: MartinPacker Blog: https://www.ibm.com/developerworks/mydeveloperworks/blogs/MartinPacker From: Mark Zelden <m...@mzelden.com> To: IBM-MAIN@listserv.ua.edu Date: 21/04/2014 19:19 Subject: Re: SORT ando MEMLIMIT best practice Sent by: IBM Mainframe Discussion List <IBM-MAIN@listserv.ua.edu> On Mon, 21 Apr 2014 11:44:01 -0500, Paul Gilmartin <paulgboul...@aim.com> wrote: >On Mon, 21 Apr 2014 07:01:50 -0500, Tom Marchant wrote: > >>On Fri, 18 Apr 2014 14:07:29 -0500, Paul Gilmartin wrote: >> >>>Are there separate pools of real storage for above the bar and below the bar? >> >>Pools? No. Pools are a software concept. >> >>Real storage with real addresses < 2 GiB are below the bar. >>Real storage with real addresses > 2 GiB are above the bar. >> >ITYM ">= 2 GiB" > >But what do you call real storage with a real address = 3 GiB or >thereabouts? I understand that for historic reasons, pertaining >only to z/OS, not other OSes, 2 GiB <= virtual address < 4GiB >is prohibited, and GETMAIN (STORAGE?) for even 64-bit >addressable storage will not return storage in that area. But >why? What harm would befall if it did? > Search the archives. That hasn't been true for quite some time now. 64-bit Java used it first, but it isn't restricted to Java. I don't know if anything else is using it at this point. The harm / fear was misinterpreting 31-bit addresses as 64-bit addresses in 64-bit programs processing 32-bit address words that had the high order bit set on either unintentionally (leftover garbage) or intentionally for something meaningful. Mark -- Mark Zelden - Zelden Consulting Services - z/OS, OS/390 and MVS ITIL v3 Foundation Certified mailto:m...@mzelden.com Mark's MVS Utilities: http://www.mzelden.com/mvsutil.html Systems Programming expert at http://search390.techtarget.com/ateExperts/ ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN Unless stated otherwise above: IBM United Kingdom Limited - Registered in England and Wales with number 741598. Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
