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From: Carel-Jan Engel <>
Date: Tue, 29 Jun 2004 21:37:46 +0200
Message-Id: <>

At 03:12 PM 6/29/2004 -0400, you wrote:
>I have setup production database full replication on seconday box in
>READ-ONLY MODE.Users are accessing the box boxes for DMLand select on
>PRODUCTION and select for secondary box.In case of disaster (suppose
>production database are having problem like disk failure ,controller failure
>etc) can I make READ-ONLY MODE database to READ-WRITE mode.
>Here is my problem:
>I have 2 identical box name db01 and db02.On db01 production instance is
>running.I want to use processing capacity of db02 24x7.I want to setup
>replication in such a way that in case of disaster (failure of db01) can we
>switch to db02 with minimun outage.
>Client don't want standby or dataguard solution.

What version are/is your customer you on? OS? How much is 'minimum outage'? How much data-loss is allowed? Is it abig database? What are the arguments against Standby/Data Guard?

On Oracle 7 I implemented a home-grown DR configuration based on triggers. This was usefull for an underused database on an overpowered serverd. Basically there was a small table storing the actual state of the database. It was standby all the time, forced so by some custom code in the dbstart script. Pre-insert/update/delete triggers prevented anyone from changing colums, except the replication-user. Replication was performed asynchronously. Failover meant just changing the 'active state' in the special table and go for it.

Later, in 8i, this was migrated to an Advanced Replication solution. This site is out of sight now.

Data Guard with Logical Standby _can_ help, but with quite a few constraints. I've setup a similar configuration, however, There 'was a Physical Standby for DR, and a Logical Standby for reporting. I wouldn't go for the LSB/DR combination on 9i. For 10g I haven't dobe enough investigation to give a clue. It might be better. When you are on processor licenses, you might be able to run the query/LSB on the same server as the DR/PSB database. It depends on the amount of redo that's created, and how much the server suffers from the recovery on PSB _and_ LSB together with the planned reports on the LSB.

I think it is technically spoken possible to create a replication mechanism to synchronyze db01 and db02. However, don't underestimate the amount of work for creating and testing such an environment, not to mention monitoring, management and maintenance to keep the thing up, running, accurate, etcetera....

Regards, Carel-Jan

If you think education is expensive, try ignorance. (Derek Bok) ===

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Received on Tue Jun 29 2004 - 14:31:15 CDT

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