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Re: log buffer question

From: Paul Drake <paled_at_home.com>
Date: Sat, 18 Aug 2001 07:46:00 GMT
Message-ID: <3B7E1D26.FDC65222@home.com>


Zin Zean wrote:
>
> Hello.
> I'm running 8.1.7 on Solaris 2.7. My database supports a web site.
>
> When oracle writes to the redo log file, such as when a user performs a
> commit,
> does it write LOG_BUFFER (setting in the init.ora) number of bytes? ie.
> flush the entire log buffer?
>
> Or does it only write transaction's redo buffer information?
>
> The reason I'm asking is that the top two wait events in our system is
> log file sync and log file parallel writes. Since these two events have
> waits
> on the same order of magnitude I'm assuming that we're writing to the
> redo log at a high rate b/c of the number of commits in our system.
> And we have LOG_BUFFER set to 512K and our redos at 10M we are
> seeing 100's of log switches in an hour. And I'm hoping that if we
> reduce LOG_BUFFER the log switch frequency will go down.
>
> Thanks.

Have you looked into what code is producing the most redo generation? Some newer structures allow for less redo generation, such as global temporary tables.
Maybe your developers have written in multiple update statements that could instead be included in insert statements. Maybe you are having lots of deletes that could instead be performed as truncates.
I've read that if you are running in archivelog mode, that oracle can use the members of an online redo log group for archiving in a round-robin fashion.
Is your disk configuration such that the currently active online redo log is on a different controller/set of disks from the redo log that is being archived?

Paul Received on Sat Aug 18 2001 - 02:46:00 CDT

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