RE: AS400 allowing 24 hour availability

We perform two way mirroring between three systems here.  All three system
can add/update/delete records from our transaction file.  Two of the systems
never, well hardly ever, get backed up or IPL'd.  They perform most of the
transaction processing.  We have been doing this for many years.  It is not
an easy task.  We are currently performing this at an application level for
one file, and a newly written trigger event on a second file.  The trigger
one is my recommended way of approaching this.

Basically the trigger program looks at the firing program and if not the
mirror poster, writes a record to a trigger results file that has the
trigger input data structure, (before and after image...).  Now a trigger
poster reads this result file and send the data to each of the remote
systems via ICF.  Then receiving end of the ICF can update the actual file
on the remote system, thus pulling the trigger on that system.  You must
make sure that the trigger program ignores the actions from the receiving
ICF program or you will get an endless loop going.

The hard part is having the sending ICF program process the trigger results
program and wait for a new record to be written.  We are still working out
the processing of the result file trying to eliminate the need to compress
deleted records and still sit at EOF Wait.  Re-Use deleted record, Force
write = 1 and wait record *nomax just does not like to work the way we want
it to.  We have a complex work around using data queues, data areas and
timestamp but I do not like the way it is working.


Hope this points you in the right direction.


Christopher K. Bipes     mailto:ChrisB@Cross-Check.com
Sr. Programmer/Analyst   mailto:Chris_Bipes@Yahoo.com
CrossCheck, Inc.         http://www.cross-check.com
6119 State Farm Drive    Phone: 707 586-0551 x 1102
Rohnert Park CA  94928 Fax: 707 586-1884

*Note to Recruiters
Neither I, nor anyone that I know of, is interested in any new and/or
exciting positions. Please do not contact me.


-----Original Message-----
From: Christina Beneteau [mailto:CBeneteau@intermatic.com]
Sent: Tuesday, November 02, 1999 10:56 AM
To: 'MIDRANGE-L@midrange.com'
Subject: AS400 allowing 24 hour availability



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.

        Christy Beneteau
        Intermatic
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