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RE: replicating an I-series home-grown application to a .net platform



fixed

I'm not disagreeing Buck, just pointing out the obvious.
Data Warehousing was implemented to retain duplicate (redundant) data.
I had this argument back in the 1980's and 90's.


Norm Dennis

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Buck Calabro
Sent: Saturday, 6 October 2012 1:21 AM
To: midrange-l@xxxxxxxxxxxx
Subject: Re: replicating an I-series home-grown application to a .net
platform

On 10/5/2012 11:08 AM, Stone, Joel wrote:

OK I'll bite - could you please share what some of the major gotcha's were
with the home grown replication systems that didn't work so well?

1) The 'two of everything' problem. You have two database schemas, two
development teams, two maintenance schedules, two upgrade schedules, two
management teams with different priorities. From now on, whenever one side
wants to change, the other side will need to be consulted.

2) The 'separate but identical' problem. The actual mechanics of
synchronising two databases are not trivial. For example, what happens when
SQL Server is offline for backups, or Patch Tuesday or because the breaker
tripped in the server room? Things happen, one of the machines is going to
be unavailable when the other one wants it. This will force you to create a
process to verify that the databases are in sync. Which probably means that
both databases will need to be taken offline. Of course, once you find an
out of sync condition you'll need a process to re-synch.

--buck
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