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Guidelines for Sizing Redo Logs for an Oracle Database

If redo logs are too small, then frequent log switches occur, creating resource-intensive Oracle Database check-pointing in which all of the dirty buffers are flushed. A range of 10 to 15 minutes or longer for log switching is preferable under a normal OLTP (Online Transaction Processing) load. However, during periods of heavy DML (data manipulation language) activity, such as during large Siebel EIM loads or upgrades, the logs might switch more frequently than every two minutes. When this occurs, overall database performance suffers as a result.

You can check the frequency of this operation either in the alert log or by querying v$loghist. It is best to use verification when there is the greatest activity and the heaviest load on the database.

If this activity occurs too frequently, then drop and re-create individual redo log groups with larger sizes. A suggested minimum size is 300 MB.

This topic is part of Configuring an Oracle Database for Siebel Business Applications.