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From: lusol@vax1.cc.lehigh.edu
Newsgroups: comp.arch
Subject: Re: What you need for crash recovery
Message-ID: <195.27b13234@vax1.cc.lehigh.edu>
Date: 7 Feb 91 15:55:47 GMT
Organization: Lehigh University
Lines: 43


     Jim Giles talks about U*X job recovery after a system crash, line
disconnect, or a program error such as a divide fault.  The various replies
indicate that U*X does a poor job in these situations, athough some flavors can
handle some of these situations properly.

     For instance Dik T. Winter mentions that UNICOS has automatic job
recovery after a crash, and Colin Plumb mentions undump and Mach's macho file
format for recovering an aborted job.

     But it seems there is NO CONSISTENCY in the U*X world with regard to job
recovery in general.

     There is an operating I use that handles all of these situation very
nicely.

        1) Job recovery after a system crash
          The operating system supports active job recovery, there is no
          need to periodically write checkpoint files on a job by job
          basis. It even recovers after most hardware failures except a
          loss of power to the machine room.  With this feature you can
          deadstart the machine at any time for whatever reason and not
          lose your ANSYS and ADINA grinders.

        2) Job recovery after a line disconnect
          When you login the operating system automatically displays a
          list of your detached jobs.  You either select a detached job
          or continue your current session.  There is no way another user
          can gain control of your job.

        3) Program recovery after a fault
          Run under control of the debugger and you can change the necessary
          variables and restart the job.  Simple.  No undumping and converting
          core files to executables.

     My question:  what is the situation in the U*X world with regard to these
three problems?  Which flavors can do what?  Is there any flavor that handles
these situations as nicely as CDC's NOS/VE OS (-:?

Steve

Lehigh University Computing Center
Stephen.O.Lidie@CDC1.CC.Lehigh.EDU