Re: Redo-Log Archiv Problem

"Kathinka Diehl" <kathinka_at_rrr.de> wrote in message news:8k4hbs$1p6lr$1_at_ID-6887.news.cis.dfn.de...
>
> Peter Miller <p.miller_at_brocom.de> schrieb:
> >
> > Thread 1 cannot allocate new log, sequence 4185
> > Checkpoint not complete
>
> I just kown this message, perhaps the other is a following error. And this
> one is easy to remove: You just have to use larger redo log files or more
> redo log groups.
>

Seems to be a popular suggestion, this 'use larger redo log files' one. It won't help at all. If you have larger logs, they take longer to switch away from, but they then take longer to checkpoint... which puts you back at square one. The only cure is to add extra log groups, so that the checkpoint has a chance to complete before you end up switching back to an earlier log file. In other words, it's not the size of what you've got that matters but how many of 'em!

That's not to say that size is totally irrelevant of course: you control the frequency of checkpointing by altering the size of the logs. Bigger=less frequent, smaller=more frequent.

Personally, for ultimate performance reasons, I would recommend absolutely enormous redo logs that never switch, and schedule a manual 'alter system switch logfile' command in the dead of night. You then get one almighty checkpoint that has plenty of time to complete before business cranks up again the next day. This only works on non-24/7 database of course, and you also need to make sure you haven't set things like log_checkpoint_timeout or log_checkpoint_interval.

Oh, and you're then in trouble if you ever get instance failure, because recovery will take ages, but if it's performance v. recovery time, you take your stance somewhere on the spectrum and arrange things accordingly.

Regards
HJR
> HTH, Kathinka
>
>
Received on Sun Jul 09 2000 - 00:00:00 CDT