RE: Save While Active

When you are on a 24 hour telemarketing system, there is no down time. Most 
users are using the same files.  We tried all three ways.  We contacted 
Rochester.  They said, no way could we do it.  The locking of the files 
stops all transaction capability.  We had an option of locking the users 
for 45 minutes, or taking the system for 1 1/2 hours for a full Non-Sys 
backup.  Guess which one we chose.
----------
From:   PaulMmn[SMTP:PaulMmn@ix.netcom.com]
Reply To:       MIDRANGE-L@midrange.com
Sent:   Friday, January 15, 1999 7:00 PM
To:     MIDRANGE-L@midrange.com
Subject:        RE: Save While Active

>...Save While Active....
>I contacted IBM
>and they said that the library can be active, but the records have to be 
in
>sinc.  It doesn't matter which form you use.  If you have a job running
>(Inter or batch) it needs to put all of the records in a freeze while it
>saves ALL of the files being used.


Well, I understand it to work a little differently.

The system needs to obtain a lock on the file(s) you are backing up.  Once
the system has a lock, it is, effectively, journalling your file(s).  Once
the system has its lock, updates from user applications are possible,
although there is some system overhead that degrades performance.

The system backs up your file(s), then applies all of the journal changes
to the file.  There are several options to tell the system what level of
synchronization you need:


Sync on a file-by-file basis:  Each file is backed up, 1 by 1, as the
system obtains a lock on it.

Sync on all files being backed up:  All files are backed up after the
system obtains a lock on all of them, at the same instant.  This means that
the system (and users) will wait until that magic moment when all files are
'quiet,' and the machine can grab its lock.  After that point, updates are
possible (the "While Active" part) while the group of files is backed up.
Makes sure the order header and order detail files are synched at the same
instant in time.

Sync on an entire library.  Same, but every object.

Sync on a group of libraries.  Even worse, as far as waiting for a lock is
concerned.


This means that, even though you can backup while activity proceeds, you
should still wait for a 'quiet time' before proceeding.

--Paul E Musselman
PaulMmn@ix.netcom.com


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