Re: number of redolog groups

"Daniel Morgan" <damorgan_at_x.washington.edu> wrote in message news:1068225157.763394_at_yasure...
> Robert wrote:
>
> >Hi,
> >
> >Is there any reason to have more than two redolog groups in NOARCHIVE LOG
> >mode?
> >
> >Thanks in advance.
> >
> >
> >
> Assuming based on the NOARCHIVE LOG mode that data recovery is not a
> priority ... no.

Sorry Daniel, that's not correct. In noarchivelog mode, there is still nevertheless a checkpoint issued at each log switch, and with only two log groups to hand, it is entirely possible to fill up the second log before the first one has been checkpointed successfully. And if that happens, your database will stall until DBWR and CKPT catch up.

Having more online log groups will therefore buy these two processes the time needed to finish the checkpoint, for the log status to therefore change from 'ACTIVE' to 'INACTIVE' and therefore for the recycling of redo logs to proceed without a database stall now an then. So yes, there still is a use for more than two online log groups, even in noarchivelog.

It's for that reason that I *always* suggest three logs should be considered the minimum practical number of online logs.

Regards
HJR Received on Fri Nov 07 2003 - 12:55:30 CST