On Mon, 1 Oct 2007 10:56:34 -0700, Rankin, Bob wrote: >Our production environment is running OS390 V2R4 (9708 PUT). My management >wants to purchase a Z9 to replace our aging Multiprise 2003-125 and move our >existing OS to run on the Z9. While we know that OS390 V2R4 has not been >certified to run on the Z9, my management thinks it possible that it might >work anyway. Personally I don't think this is feasible but IBM has done >stranger things in the past. > >Can anyone out there provide more specific information regarding this topic. >While I know that there are significant instruction set differences, perhaps >V2R4 may not encounter them, I don't know. > >Has anyone done this? > >Does anyone know what will happen if we attempt to do this? Search the archives for [(Mulder) and (purge)] and you should find this: "z890, z990, and z9 machines have a 2-level TLB. Nothing lower than OS/390 2.10 will run reliably on a machine with a 2-level TLB because lower releases than 2.10 do not do some of the necessary TLB purges. I have heard some speculation that you might be able to get around this by running an older MVS under VM, with the following VM trace: "#CP TRACE IPTE RUN NOTERM "Of course, this would cause some performance degradation, since VM would intercepting and simulating every IPTE for this virtual machine. I don't know of anyone who has tried this. It was just some hall talk with a VM developer. "There may be other issues that would prevent an older MVS from running on a modern machine, such as missing support for a larger storage increment size. The storage increment size might also be avoided under VM if the virtual machine does not have too much real storage defined - I think VM simulates the increment size but I wouldn't swear to that." ...which leads me to believe that you can expect 'difficulties' (at minimum) unless you are running your OS/390 2.4 system under z/VM - and maybe even IF you are running under z/VM. (It was just hallway talk, after all.) Jim's post was addressing a jump from a newer-than-your machine to a z/9-BC and he posted it back in (or around) February. (Thanks, as always, Jim!) -- Tom Schmidt Madison, WI
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