Re: Log Switching

Jeremiah Wilton wrote:

> Hmm, what is the LOG_CHECKPOINT_TIMEOUT parameter for then? Wouldn't it
> just do the same thing as your cron job?

A checkpoint is not the same as a log switch. Setting LOG_CHECKPOINT_TIMEOUT merely forces the database to perform extra checkpoints; it does not force a log switch to occur. A checkpoint occurs when a log switch occurs by definition, but the reverse is not true.

Setting LOG_CHECKPOINT_TIMEOUT does causes checkpoints to occur at a specified number of seconds. When a checkpoint occurs, LGWR writes the contents of the redo log buffer to the online redo log. Only if the checkpoint is the result of a log switch will ARCH generate an archive log file from the previously active online redo log file (once the file is marked as inactive in v$log).

To the best of my knowledge, there is *no* parameter or configuration setting in Oracle7 or Oracle8 that can be configured to force a log switch to occur. Oracle recommends in the performance tuning classes for Oracle7 and Oracle8 that you configured LOG_CHECKPOINT_TIMEOUT and LOG_CHECKPOINT interval so that checkpoints occur only when the online redo logs are switched.

Jonathan Ingram
jonathan.ingram_at_miname.com
Remove the first "m" from "miname.com" to reply. Received on Mon May 03 1999 - 15:50:10 CDT