Re: WAL and backup recovery

On Wed, 23 May 2001, Tom Lane wrote:

> Dario Brignardello <dbrignar(at)sinectis(dot)com> writes:
> > checkpoint_segments = 1
> > checkpoint_timeout = 30
>
> Reducing checkpoint_segments and checkpoint_timeout is actually
> seriously counterproductive, if your problem is amount of disk space
> chewed up by WAL logs during a long transaction (such as bulk load of
> a big table). The WAL log cannot be truncated until the xact commits,
> so the checkpoints that happen meanwhile just cause log bloat. Lots
> of it, because each checkpoint causes fresh copying of modified pages
> into the WAL log.

Hi Tom,
in the manual it mentions that the defaults are checkpoint_segments=3 and checkpoint_timeout=300 and a checkpoint occurs for whichever of the two comes up first. If I change in postgresql.conf checkpoint_segments=10, will the default checkpoint_timeout=300 be ignored or should I increase that as well. I mean, will checkpoint_timeout be still in effect, because if so, then the increasing only checkpoint_segments is useless.

thanks in advance,
thalis

>
> Try increasing those numbers, not decreasing them. Maybe 10/600 or so?
>
> Also, if you are short on disk space for WAL, increasing wal_files isn't
> such a great idea either.
>
> regards, tom lane
>
> ---------------------------(end of broadcast)---------------------------
> TIP 2: you can get off all lists at once with the unregister command
> (send "unregister YourEmailAddressHere" to majordomo(at)postgresql(dot)org)
>