Re: Logon during night backup on tape

The major problem with "Save-While-Active" is ensuring that the
transactions are synchronized during the backup. For example, suppose
you have a program that saves a particular transaction in three
different files (and records). It could happen that your backup saves
FILE1 sans RECORD1 and, after that, your app runs and writes the three
records. A short time later, your backup saves FILE2 and FILE3. At
that moment, your backup data is inconsistent.

Save-while-active is the way to go. Synching isn't a problem if you
approach the shutdown properly. If you temporarily end QINTER and quiesce
subsystems that might have jobs with record locks it's pretty
straightforward. We went from having the system down for about 2.5 hours
to about 20 minutes. (That was on our old 720.) Ending jobs and shutting
things down is the hardest part. Once that's done you can have a job that
sits in its own job queue monitoring a message queue waiting for the
message that the checkpoint has been established. After that, you can
resume normal operations. If you try to start a SWA in an uncontrolled
manner then you probably will have issues. It's too bad that Al Barsa
isn't around to campaign for save-while-active. He really helped me with
it.

Having said that, we now have zero downtime. We just end mirroring to our
DR-system and do the backup on it.


Dave Parnin