• Subject: Re: AS400 allowing 24 hour availability
  • From: Larry Bolhuis <lbolhui@xxxxxxx>
  • Date: Tue, 02 Nov 1999 22:03:38 -0500
  • Organization: Arbor Solutions, Inc

Christina,

  It has been mentioned to 'write your own'.  In the days prior to being
DataMirror BPs I tried that.  No Way!  I'm not going to debate the relative
merits of DataMirror and it's competition but suffice to say we chose to
represent DataMirror.

  You can certainly set up System A to mirror to System B.  You can suspend
mirroring (any transactions queue up) while you do backup on System B. You can
certainly run any nightly reporting on System B so long as no updates are
required, thus giving you additional resources.

  If you want to do 'two way' mirroring then you are certainly into the Advanced
Course.  DataMirror supports this in two ways, you can switch the mirroring
direction (allows updates basically on one system at a time) or you can add exit
programs to do the DB updates, which you code to update the appropriate fields.

  Consider updates to both databases.  If you update file A on system A and file
B on system B and the mirroring mirrors them respectively you can see this
presents no problems.  Now if you update file A on both systems then you have
some work to do.  If you can be assured that system A only updates field 1 and
system B updates field 2 then your exit program will relatively simple.  If both
update the same field then you must code for that in your exit program.  I won't
go into the permutations of the possibilities that you will face but there are
several.

  You can also add hardware/software between the two systems to utilize the B
system as a hot backup to A.  This increases the complexity some but also the
value.

  HTH - Larry

Christina Beneteau wrote:
> 
> Christy
> 
>         We are in the process of determining the best way to accomplish
> 24 hour access to our AS400.  Currently access is denied for about 4
> hours a night.  This is due to system backup and nightly processing jobs
> such as billing.  At month end we have about 12 hours of down time for
> the users.  While some of the restriction of access is due to nightly
> back up over half of the time is because of our ERP solution, BPCS.
> 
>         I have been looking into how we could mirror the database.  Once
> mirrored then unlink them so that backup and nightly processing could be
> ran over the mirrored database.  Data changes would continue in the
> original database.  After the backup and nightly processing then these
> databases would need to be brought back into sync.  There would be
> changes in both databases, is there such a thing as two way mirroring?
> Has anyone done this?  I have been told that in order for us to change
> the database that the application is running over that we would need to
> use ASPs.  I have had a hard time finding people that have actually done
> this.  Any possible solution that I have seen approaches it either from
> the software or hardware side but not using a combined approach.  I
> appreciate any comments anyone has on this.  Thanks.

-- 
Larry Bolhuis         | What do You want to Reload today?
Arbor Solutions, Inc  | Don't throw your PC out the window,
(616) 451-2500        |  throw WINDOWS out of your PC.
(616) 451-2571 -fax   | Two rules to success in life:
lbolhui@ibm.net       | 1. Never tell people everything you know.
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