Oracle-L: Online redo sizing and parameters

From: O'Neill, Sean <Sean.ONeill_at_organon.ie>
Date: Tue, 07 May 2002 05:38:29 -0800
Message-ID: <F001.00459D11.20020507053829@fatcity.com>

I'm looking to resize our online redo logs for a particular app and am somewhat confused about the appropriate settings. The current config is 4 groups (2 members each) of 5Mb size. We cycle through a daily average of 750 logs in a 22 hour period. During a more intensize daily batch window of 5 hours there is an average of 100 per hour switches i.e. two thirds of switches are occuring during the batch window.

I'm planning to resize the online redo logs to 120Mb based upon rationale of 500Mb per hour in batch window and 4 groups. So switching will happen apporox every 15 minutes. Some Oracle documentation suggests 1 switch per hour is best and others one switch every 30 minutes. So question 1: Does this proposed resize make sense?

Our current log_checkpoint_interval = 10,000 which means a checkpoint at approx 39Mb given it's a Win 2k OS with it's OS block size of 4096. So question 2: Does it make sense to leave this setting as is and have approx 3 checkpoints per each redo (timewise every 5 minutes) or is there a better value and why? (Support suggested setting to zero, i.e. effectively ignore!).

The log_checkpoint_timeout is currently 1800. Support suggested setting this to zero but the reference manual suggests that this should not be done!.
So final question: What would the best value be given the log_checkpoint_interval would probably have a checkpoint every 5 minutes using heavy processing?.

Your considered opinions/input re above would be much appreciated.

Seán O' Neill
Organon (Ireland) Ltd.
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Author: O'Neill, Sean
  INET: Sean.ONeill_at_organon.ie

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Received on Tue May 07 2002 - 08:38:29 CDT