Checkpoint/Restart

[Bob Rahe]

   Barry Shein hits the nail right on the proverbial head about the tail
wagging the dog - the checkpoint restart code becoming the overwhelming
decision maker in the system.

  I don't know about the historical question ala OS/MVT doing this warm
restart but Burroughs (now Unisys) did this stuff back in the '70s with the
B7700 class mainframes.  The demo was to have a 2x2 system (2 procs and 2 io
procs) and walk up to a running system and pull a proc card out (!).  It would
mostly do the right thing.  It also would, about 75% of the time, restart after
a power failure with only 'currently running on the proc' processes not coming
back, and even those would sometimes work.  They seemed to abandon this as the
MCP got more elaborate for the same reason TOPS dropped it - it seemed all
kinds of nice new features couldn't be made to work if they had to be restart-
able.  Impressive when it worked tho - for the '70s anyway.


      Bob