RE: Oracle MAA and active-active replciation between site

  • From: "Pradeep Chetal" <Pradeep.Chetal@xxxxxxxxxxxxxx>
  • To: "Yavor Ivanov" <Yavor_Ivanov@xxxxxxxx>
  • Date: Mon, 11 Aug 2008 16:29:11 -0400

Yavor,

If we are OK with few hours of delay between the 2 sites, is there other
software that works to keep the 2 sites in sync?

Some folks I talk to, do NOT like Oracle Advanced Replicatiom.

What about Golden Gate software or IBM's Data mirror?

-- Pradeep

-----Original Message-----
From: Yavor Ivanov [mailto:Yavor_Ivanov@xxxxxxxx] 
Sent: Friday, August 01, 2008 6:57 AM
To: Pradeep Chetal
Cc: oracle-l@xxxxxxxxxxxxx
Subject: RE: Oracle MAA and active-active replciation between site


        The big concern about the application in replication environment
are the conflicts.
        - You should in all ways avoid updating or deleting the same row
of a table from both sites at the same time.
        - The same for the inserts. Your application should not be able
to insert rows with the same primary key values from both sites. E.g. if
you have primary keys generated by sequence, one of the sites should
start with 1 increment by 5 and the other will start with 2, increment
with 5.
        - You must have primary key on all tables. This is not mandatory
from the docs, but it is always good practice, even without replication.
        - You should design all triggers carefully - when there is an
insert in a table on one site, the trigger may make some things like
inserting/updating/deleting on other tables. Then when this is
replicated to the other site, there will be insert again, but the
trigger should not fire again.
        - When there is a conflict, a whole transaction is not
replicated. Even if you do not care for this problematic row in this
table, a conflict on a row of a table will block the whole transaction
and you have to resolve it.
        - If you decide to let the replication of all following
transactions be done in spite of the conflicts, you may have lots of
anomalies in the data. In the other hand, resolving a conflict may take
some time and you may not want to block the whole replication because of
a single problematic transaction

Regards,
Yavor Ivanov
Oracle Certified Master


-----Original Message-----
From: Pradeep Chetal [mailto:Pradeep.Chetal@xxxxxxxxxxxxxx]
Sent: Friday, August 01, 2008 12:56 PM
To: Yavor Ivanov
Subject: RE: Oracle MAA and active-active replciation between site


Yavor,

In terms of wise application design, what do you recommend?

What are the big 3-4 things we should worry about?

-- Pradeep

-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Yavor Ivanov
Sent: Friday, August 01, 2008 3:05 AM
To: Pradeep Chetal; oracle-l@xxxxxxxxxxxxx
Subject: RE: Oracle MAA and active-active replciation between site


        I've done one project active-active replication using oracle's
Advanced replication. There is good documentation about this.
        There are 2 basic problems with this
                - The conflicts. You will always have conflicts on
active-active replication. Most of them can be avoided by wise
application and process design, but it will need lot of thinking. And
you will still have conflicts you cannot avoid and cannot resolve
automatically
                - The burden. It is much harder for administration.
Adding a simple column is pain in the ass, Yes, there are procedures,
but still... It is hard.
        But it really works - for 2 years now. I would consider this.

        I also have done it with "Basic replication", master -
(updateable) mvews with 12 active sites across the country (one master
in HQ). But it is even harder to support this than Advanced replication.
And the application on this project was specially built with the
replication in mind. It works for 9 years now (we started it on 8.1.5,
now all the servers are 10.2). But I would never advise this approach,
this is aged and arcane thing.

Regards,
Yavor Ivanov
Oracle Certified Master

-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Pradeep Chetal
Sent: Thursday, July 31, 2008 6:18 PM
To: oracle-l@xxxxxxxxxxxxx
Cc: Pradeep Chetal
Subject: Oracle MAA and active-active replciation between site
Importance: High



Hi,

Oracle has an MAA with

http://www.oracle.com/technology/deploy/availability/pdf/MAA_WP_10gR2_Ro
admap.pdf

However, one of our clients would like to have active-active replication
between remote sites, so that each site can be used.

Have you done this? What software did you use?

Also, what are the limitations on schema, if any to do this?

Thanks in advance,

-- Pradeep




Pradeep Chetal
Sr. Director - Infrastructure Architecture



Mformation Technologies Inc.
Switchboard: +1 732 692 6200



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Visit WWW.MFORMATION.COM and see how the MFORMATION SERVICE MANAGER can
help you to transform your business


Please consider the environment before printing


 
Visit WWW.MFORMATION.COM and see how the MFORMATION SERVICE MANAGER can help 
you to transform your business


Please consider the environment before printing
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