Re: Oracles streams stability for 9.2.0.5

<dbaplusplus_at_hotmail.com> wrote in message news:1146154502.043932.51490_at_e56g2000cwe.googlegroups.com...
>I presume you are talking about logical standby database and not
> streams.
> Logical standby database requires supplemental loggng. In our case,
> several of our tables do not have
> primary key/unique index, being a third party application, we may not
> add them as well.
>
> What is your experience in the overhead of supplemental logging because
> of logical standby database.
>
>
> Thanks,
>

If you have tables without unique primary keys, then when you enable supplemental logging at the database level - which is required for logical standby in 9i - the mechanism copies entire rows into the redo log. The overhead may be dramatic. In fact, since supplemental logging gets the 'supplement' into the redo log by creating it first in the undo you pay a double penalty.

On the other hand, you're already using Shareplex - so the overheads are likely to be similar, even though the mechanisms will be very different. Best bet is to run a fair test, watching for changes in logical I/O and physical I/O as well as waits for lgwr to complete.

-- 
Regards

Jonathan Lewis
http://www.oracle.com/technology/community/oracle_ace/ace1.html#lewis

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