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From: Richard Huxton <dev@archonet.com>
Organization: Archonet Ltd
To: Florian Litot <flitot@besancon.sema.slb.com>, pgsql-general@postgresql.org
Subject: Re: log file?
Date: Tue, 5 Nov 2002 13:17:04 +0000
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On Tuesday 05 Nov 2002 12:48 pm, Florian Litot wrote:
> At 12:47 05/11/02, Richard Huxton wrote:
> >How many files are there in pg_xlog and what dates do they have?
> >What are the WAL settings in your postgresql.conf file?
> >Do you have any clients that have been running a long time?

> i have got 66 files
> i have got a new file to 16 minutes

> wal_files =3D 64 # range 0-64
> #wal_sync_method =3D fsync   # the default varies across platforms:
> #                          # fsync, fdatasync, open_sync, or open_datasync
> #wal_debug =3D 0             # range 0-16
> #commit_delay =3D 0          # range 0-100000
> #commit_siblings =3D 5       # range 1-1000
> #checkpoint_segments =3D 3   # in logfile segments (16MB each), min 1
> #checkpoint_timeout =3D 300  # in seconds, range 30-3600
> #fsync =3D true
>
> it's standard
> i make some insertion i make 1 insertion every 2 seconds

I don't think I can explain better than by quoting from the manual (for the=
=20
full details see the WAL implementation and configuration sections):
"The number of 16MB segment files will always be at least WAL_FILES + 1, an=
d=20
will normally not exceed WAL_FILES + MAX(WAL_FILES, CHECKPOINT_SEGMENTS) + =
1.=20
This may be used to estimate space requirements for WAL. Ordinarily, when a=
n=20
old log segment files are no longer needed, they are recycled (renamed to=
=20
become the next sequential future segments). If, due to a short-term peak o=
f=20
log output rate, there are more than WAL_FILES + MAX(WAL_FILES,=20
CHECKPOINT_SEGMENTS) + 1 segment files, then unneeded segment files will be=
=20
deleted instead of recycled until the system gets back under this limit. (I=
f=20
this happens on a regular basis, WAL_FILES should be increased to avoid it.=
=20
Deleting log segments that will only have to be created again later is=20
expensive and pointless.) "

Given a wal_files setting of 64 you're always going to have 65 files. Keep =
an=20
eye on it and see if the number of files keeps increasing - if not, you don=
't=20
have a problem. If you want to reduce the number of files, reduce wal_files.

--=20
  Richard Huxton