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Re: Logical Standby Issues (cont.)

From: Alex Gorbachev <>
Date: Tue, 8 Aug 2006 08:08:32 +0200
Message-ID: <>

We put in crontab restart of apply service every now and again. This was done because of regular ORA-600 otherwise. Perhaps, this technique can also improve performance. ;-)
Also, I missed in the thread if you use parallel apply - we saw that some type traffic can be applied in parallel very well and some are better running serial.

2006/8/8, Mark Strickland <>:
> I continue to beat this possibly-dead horse...
> Over the past two weeks, I've been testing Logical Standby performance
> in,, and on Solaris 5.9. I have a table
> with 1,000,000 rows, I add a new column to the table in the primary
> database, then set that column equal to another column and commit.
> Takes about 3 minutes in the primary. That update is converted into
> separate row-level update statements in the logical standby. Fine. I
> accept that. However, it takes longer and longer to fill up a redo
> log as SQL Apply chews through the load, about 10 seconds longer per
> log on average (10-Mb redo logs). So it starts out taking about 20
> seconds to fill up a redo log (as measured by time between log
> switches reported in the alert.log) and each one takes on average 10
> seconds longer until the last one takes about 8 minutes. I've graphed
> it and the curve is linear with a few shallow dips here and there.
> The total update in the logical standby takes about four hours to
> complete. If I simply run 1000000 update statements from a SQL
> script, it takes 50 minutes. That's 1000000 unique SQL statements,
> btw. I can live with 50 minutes compared to 3 minutes. I can't live
> with 4 hours compared to 3 minutes. I'm thinking maybe there's a
> chain/linked list/whatever of some sort that gets longer and longer
> and has to be chased down to the end with each update. That sort of
> analysis is getting beyond my technical skill. Perhaps those of you
> who are stronger technically might have insight. At least something I
> can tell Oracle Support to look into. Not getting far with Oracle
> Support. I have three SRs open regarding Logical Standby right now.
> Thx.
> Mark
> --

Best regards,
Alex Gorbachev
Received on Tue Aug 08 2006 - 01:08:32 CDT

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