Re: log_checkpoint_timeout new meaning in 8i

Questioned this myself after noticing 8i logswitch checkpoints taking a LONG time. There is a new parameter you might look at: fast_start_io_target. Also look at v$instance_recovery, it shows which parameter (log_checkpoint_timeout, log_checkpoint_interval, fast_start_io_target) takes priority for controlling checkpoints.

I ended up setting both log_checkpoint_timeout and log_checkpoint_interval to zero. Then fiddled with fast_start_io_target until the checkpoint intervals seemed reasonable. Note that these checkpoints don't appear in alert.log, I dunno why.

Still bewildered, but things appear to be working much better.... suzy

> "Koivu, Lisa" wrote:
>
> hello all,
>
> I've got LOG_CHECKPOINT_TIMEOUT set to 1800 (30 minutes) in one of my
> databases. I also have LOG_CHECKPOINTS_TO_ALERT set to true.
> However, every morning I look at the archive logs and I see that 1.
> the logs haven't switched since the nightly batch quit and 2. there
> are no checkpoints in the alert log since the log switch. This makes
> me a little nervous.
>
> It seems that LOG_CHECKPOINT_TIMEOUT is not working. However, I find
> this on metalink that kind of explains it.
>
> The parameter log_checkpoint_timeout has been re-interpreted. In prior
> releases, every log_checkpoint_timeout seconds, Oracle started an
> interval checkpoint. Starting with Oracle 8.1, log_checkpoint_timeout
> will be interpreted to mean that the incremental checkpoint should be
> at the log position where the tail of the log was
> log_checkpoint_timeout seconds ago. In other words, the incremental
> checkpoint should lag the tail of the log by no more than
> log_checkpoint_timeout seconds worth of redo.
>
> I don't quite understand. Can someone paraphrase this? Does this
> mean that every LOG_CHECKPOINT_TIMEOUT seconds it makes sure that
> there is no redo that hasn't been written to disk that is more than
> LOG_CHECKPOINT_TIMEOUT seconds old? In other words, it checks to see
> if a checkpoint is necessary instead of just doing it?
>
> Thanks
>
> Lisa Rutland Koivu
> Oracle Database Administrator
> Qode.com
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Received on Thu Jan 04 2001 - 15:11:57 CST