From: arne@vajhoej.dk   
      
   On 9/16/2025 5:38 PM, David Wade wrote:   
   > On 16/09/2025 22:00, Arne Vajhøj wrote:   
   >> On 9/16/2025 4:47 PM, David Wade wrote:   
   >>> On 16/09/2025 18:46, Simon Clubley wrote:   
   >>>> Especially given that z/OS is actually several years older than VMS   
   >>>> and is still going very strongly indeed.   
   >>>   
   >>> I don't believe its as strong as you believe. Perhaps the Z platform   
   >>> is, but z/OS is pretty much limited to traditional big banks and   
   >>> airline reservation systems. These systems are all much larger that   
   >>> most VMS systems so migration away is harder and riskier.   
   >>   
   >> I am not sure that the attrition rate for z/OS is less than for VMS.   
   >>   
   >> But they started at a way higher point, so they are still at a higher   
   >> point.   
   >>   
   >>> Another notable feature of Z hardware is the virtualisation   
   >>> technology inherent in the "hardware". So it all comes with multiple   
   >>> Logical PARtitions or LPARs which despite their name are more like   
   >>> physical partitioning of the hardware, and zVM which uses the "Start   
   >>> Interpretive Execution" (SIE) instruction to create Virtual Machines.   
   >>>   
   >>> DEC never had anything like this.   
   >>   
   >> I always considered Alpha Galaxy to be somewhat similar to LPAR.   
   >   
   > Isn't that the layer that translates Vax instructions?   
      
   No - that was VEST.   
      
   >                                                           LPARs allow   
   > multiple operating systems to be run. Could you ever run VMS and ULTRIX   
   > at the same time on the same Alpha box.   
      
   Galaxy allowed you to run multiple instances of VMS   
   on the same Alpha (GS and ES only).   
      
   But I believe there was both hard and soft partitioning   
   and soft partitioning was VMS only, but hard partitioning   
   supported both VMS and Tru64 (Ultrix was VAX and MIPS only).   
      
   Disclaimer: long time ago and I may misremember some of it.   
      
   Arne   
      
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