Re: Way to much log switching!!!

On Wed, 30 Jun 2004, Mark Moynahan wrote:

> Currently, we have an ODS system with 3 redo log files sized at 200M each.
> Looking at v$log_history, the logs are switching every 1 to 2 minutes. If a
> 200M log switches at 2 minutes then a 400M log should switch in 4 minutes
> and 1G log should switch in 10 minutes. I've recommended to size the redo to
> 1G along with determining what is causing all the redo with Logminer. Is 20
> minutes a good rule of thumb to go by when seeing how often the redo logs
> switch?

If checkpoints and archiving are keeping up, then I can't think of a
good reason logs shouldn't switch every 2 minutes.

You don't need logminer to find the redo culprit, just this SQL:

select module, osuser, sql_hash_value, value / (sysdate - logon_time) redo
from v$session s, v$sesstat ss, v$statname sn
where s.sid = ss.sid
and ss.statistic# = sn.statistic#
and name = 'redo size'
order by redo;

--
Jeremiah Wilton
http://www.speakeasy.net/~jwilton
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