ADSM-L

Db Mirroring question

1996-02-20 10:48:17
Subject: Db Mirroring question
From: Jerry Lawson <jlawson AT ITTHARTFORD DOT COM>
Date: Tue, 20 Feb 1996 10:48:17 -0500
Date:     February 20, 1996            Time:    09:54
From:    Jerry Lawson
    ITT Hartford Insurance Group
    (203) 547-2960    jlawson AT itthartford DOT com
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I thought we knew what was going on with this question, but then we read the
I thought we knew what was going on with this question, but then we read the
manuals.......  :-)

We have been mirroring our DB, but since the DB resides on an STK Iceberg, we
have decided that the benefits of mirroring are outweighed by the cost of the
extra DASD required.  So..... we decided to remove the mirroring.  We read
through the Admin GUIDE on reducing the DB, and also in Admin reference, and
in that volume I found the following statement:

   "You cannot delete the last synchronized volume in a copy set unless the
information on the volume can be moved by ADSM to other synchronized volumes
in the database"

The Glossary definition of Synchronized Copy Status helps to add to our
confusion.  As I read this, when a DB volume is mirrored (a copy is added),
then it becomes Synchronized.  (??)  If that is true, then based on the quote
above, is it even possible to delete the mirror once it has been added?  Some
of the confusion depends on the definition of a mirror - If i have 2 DB
volumes (DB1 and DB2), and two mirrors (DBA and DBB), is the synchronization
done between pairs of volumes (DB1 and DBA)? The manuals indicate that the
mirror can be larger than the original DB - does this add to the problem.

By the way, our mirror is only 1 copy per volume, not 2.

Has anyone actually deleted their mirror once they started it?

In a related (somewhat) question, the Admin GUIDE has a good description of
how to remove DB Volumes, with examples on how to reduce and delete a volume.
One question that came up, though, was found in an examination of the syntax
of the commands - The Vary command mentions the DB;  The GUI also has a button
for Vary On/Off.  Knowing how the rest of MVS works, shouldn't  the DB Volumes
be varied offline before a delete is done?

*****************************************************************************
Jerry Lawson
ITT Hartford Insurance Group
jlawson AT itthartford DOT com
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