Re: WAL and backup recovery

On Wed, 23 May 2001, Tom Lane wrote:

> Dario Brignardello <dbrignar@sinectis.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
occursfor whichever of the two comes up first. If I change in postgresql.conf checkpoint_segments=10, will the default
checkpoint_timeout=300be ignored or should I increase that as well. I mean, will checkpoint_timeout be still in effect,
becauseif 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
>
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