On Thu, 9 Dec 2010 10:36:43 -0500, Tom Marchant <[email protected]> wrote:
>Prior to that, it is true that that IARV64 would never create a >memory object in the range from 2GB to 4GB. That was an arbitrary >decision intended to avoid confusion. As I understand it, there >was some concern that a user might see an address with bits 0-31 >all zero and bit 32 on and be confused. Is it a 31-bit address >with the high order bit on to signify AMODE(31) or is it a 64-bit >address? It seems to me that it hes led to considerable other >confusion. > >As to Java, this was discussed on IBM-MAIN. See, for example, >this post from Jim Mulder: >http://www.mail-archive.com/[email protected]/msg108339.html > >where he writes, >>>The range from 2GB to 32GB is set aside for a particular >>>intended user, which is the JVM. > >The way that the area is used is described in SHARE presentation >2160 from Seattle last year, titled, "Java SDK5, SDK6 and Beyond: >A Performance Update" > Additionally, in z/OS R12 the area from 32G to 288G is now reserved for system callers who ask for its use via the LOCALSYSAREA=YES parameter on IARV64 REQUEST=GETSTOR. (And isn't this entire discussion more appropriate for IBM-MAIN?) -- Walt Farrell IBM STSM, z/OS Security Design
