One problem with zero-downtime backups is the problem of knowing when to
quiesce a process.  In the case of an online session it's not so difficult,
because you can usually safely assume that a terminal read represents the
end of a logical transaction.  In the case of a batch job, however, it's not
so simple.  If your applications consistently use DBXBEGIN and DBXEND to
delimit a logical transaction, you can use a zero-downtime backup solution
with confidence.  If you do not always do so, you run the risk of your
sync-point occurring in the middle of an uncompleted logical transaction,
causing your database to be stored in a logically inconsistent state.

In short, zero downtime backup works, but it requires some discipline in
your programming practices, or at least some care in scheduling batch
processes.  The "programming discipline" can be difficult or impossible to
enforce when you have software that was not developed in-house.

-----Original Message-----
From: John R. Wolff [mailto:[log in to unmask]]
Sent: Thursday, September 12, 2002 9:08 AM
To: [log in to unmask]
Subject: MPE/iX is Aware of Native Databases for Online Backup


This week I installed the patches necessary for 6.0 to be able to perform
store-to-disk (STD).  (This is a great feature, by the way.)  As part of
this project I thought I should review the Help sections for STORE and
RESTORE to re-acquaint myself with the many options.

I was interested to note that the ONLINE backup feature of TurboSTORE works
hand in hand with both Image/SQL and Allbase/SQL, to coordinate and
facilitate a smooth backup result while applications remain active.  It
communicates with these native databases to quiesce transactions to
completion so that a sync point can be achieved, afterwhich the databases
are unquiesced and processes continue normally while the backup proceeds.
This syncing process is very short, usually less than a minute.  Naturally,
the ONLINE backup feature requires the TurboSTORE/iX 7x24 product to be
installed (which we do not have).

I realize this is not a new feature of MPE/iX & STORE, but think it is an
important consideration for some that may be contemplating migration
prospects.

I would imagine that many HPe3000 shops would have a need for this unique
feature because they cannot afford the extended downtime required for a
normal backup.  I am wondering what such users will do to substitute for
this functionality on a UNIX or Windows NT platform?  It seems to me that
this is a feature that HP-UX, etc. does not enjoy with Oracle, etc..

Any comments?

* To join/leave the list, search archives, change list settings, *
* etc., please visit http://raven.utc.edu/archives/hp3000-l.html *

* To join/leave the list, search archives, change list settings, *
* etc., please visit http://raven.utc.edu/archives/hp3000-l.html *