From: arne@vajhoej.dk   
      
   On 11/11/2025 3:57 PM, Lawrence D’Oliveiro wrote:   
   > On Tue, 11 Nov 2025 10:50:57 -0500, Arne Vajhøj wrote:   
   >> Note that even though z/OS and mainframes generally have a good   
   >> track recording regarding availability, then it is not a magic   
   >> solution - they can also have problems.   
   >   
   > Mainframes were never designed for high availability. It was normal to   
   > run them 24/7, simply to try to get as much as possible out of them   
   > because they are/were so expensive to buy. But it was no big deal if   
   > they had to be taken down for, say, an hour a week for “preventive   
   > maintenance” or to switch OSes or whatever.   
      
   24x7 vs 16x5 is not about HA - HA is about whether the system   
   can continue to serve users in case part of a box or an entire   
   box fail - 24x7 vs 16x5 is about architecture.   
      
   Once upon a time it was common to shutdown an application   
   at night and run various batch jobs, do backups etc.. z/OS   
   or VMS or Unix.   
      
   Many of the old applications still work that way. And   
   it is one of the reasons why nobody want to do a 1:1   
   conversion from Cobol or PL/I to Java or C# or whatever -   
   the application need to be rearchitected to work a different   
   way.   
      
   Arne   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)