Re: DB_WRITER_PROCESSES vs DBWR_IO

From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
Date: Fri, 09 Jan 2004 12:34:43 -0800
Message-ID: <F001.005DC4A2.20040109123443@fatcity.com>

One interpretation of increased red latch contention and log buffer space waits is that more work is being done more quickly - so the log writer can't keep up.

This could mean:

the log writer has slowed down
the database writer(s) have speeded up, so there is less time lost on write complete waits, free space waits, and (side effect) buffer busy waits.

So the symptoms could be positive or negative, and we don't have enough relevant information to say which. Depending on the nature of the application, and the number and duration of sync waits, you could address the log buffer space waits by increasing the size of the log buffer.

Are the redo latch waits allocation latch or copy latch ?

Regards

Jonathan Lewis
http://www.jlcomp.demon.co.uk

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Original Message -----

Now, the Sr DBA here is screaming about the performance since I made the change,
in particular, he says he's seeing high redo latch contention and redo log
buffer waits which he says validates his contention that we need to get back to
using DBWR_IO_SLAVES.

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--

Author: Jonathan Lewis
INET: jonathan_at_jlcomp.demon.co.uk

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Re: DB_WRITER_PROCESSES vs DBWR_IO_SLAVES