Hi every one.

I just moved (at last!) to 7.2.1. Works like a charm...
I'm suprised though by the number of WAL files.

I have 8 files where postgresql.conf says WAL_FILES=4.

What did I miss ? (I have no outstanding transaction)

FWIW, t's on UW711.

Regards,

-- 
Olivier PRENANT         	Tel:	+33-5-61-50-97-00 (Work)
Quartier d'Harraud Turrou           +33-5-61-50-97-01 (Fax)
31190 AUTERIVE                      +33-6-07-63-80-64 (GSM)
FRANCE                      Email: ohp@pyrenet.fr
------------------------------------------------------------------------------
Make your life a dream, make your dream a reality. (St Exupery)


Sun, 26 May 2002 18:55:21 +0200 (MET DST)
Olivier PRENANT <ohp@pyrenet.fr>
WAL FILES
Olivier PRENANT wrote:
> Hi every one.
> 
> I just moved (at last!) to 7.2.1. Works like a charm...
> I'm suprised though by the number of WAL files.
> 
> I have 8 files where postgresql.conf says WAL_FILES=4.
> 
> What did I miss ? (I have no outstanding transaction)
> 
> FWIW, t's on UW711.

No, you are fine.  The current GUC params are confusing. I did update
the documentation for 7.3, but I plan to reorganize those params to be
more meaningful.

Actually, I have in TODO:

  Remove wal_files postgresql.conf option because WAL files are now
  recycled 

because the param no longer controls what you think it controls.  In 7.1
WAL files where not recycled, so WAL_FILES was used to pre-allocate
files so there wasn't as much happening during checkpoint.  Now, with
recycling, there is no need.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026

Mon, 27 May 2002 17:17:58 -0400 (EDT)
Bruce Momjian <pgman@candle.pha.pa.us>
Re: WAL FILES
Hi Bruce,

Thank you for your reply. It makes a lot of sense!
However I don't really understand why we can't control the NUMBER of
files.
Are the 8 files I see a maximum usage when I reloaded the databases on the
ne system or is it some sort of "plugged in value"?

Thank you for your explanation.
On Mon, 27 May 2002, Bruce Momjian wrote:

> Date: Mon, 27 May 2002 17:17:58 -0400 (EDT)
> From: Bruce Momjian <pgman@candle.pha.pa.us>
> To: ohp@pyrenet.fr
> Cc: pgsql-hackers list <pgsql-hackers@postgresql.org>
> Subject: Re: [HACKERS] WAL FILES
> 
> Olivier PRENANT wrote:
> > Hi every one.
> > 
> > I just moved (at last!) to 7.2.1. Works like a charm...
> > I'm suprised though by the number of WAL files.
> > 
> > I have 8 files where postgresql.conf says WAL_FILES=4.
> > 
> > What did I miss ? (I have no outstanding transaction)
> > 
> > FWIW, t's on UW711.
> 
> No, you are fine.  The current GUC params are confusing. I did update
> the documentation for 7.3, but I plan to reorganize those params to be
> more meaningful.
> 
> Actually, I have in TODO:
> 
>   Remove wal_files postgresql.conf option because WAL files are now
>   recycled 
> 
> because the param no longer controls what you think it controls.  In 7.1
> WAL files where not recycled, so WAL_FILES was used to pre-allocate
> files so there wasn't as much happening during checkpoint.  Now, with
> recycling, there is no need.
> 
> 

-- 
Olivier PRENANT         	Tel:	+33-5-61-50-97-00 (Work)
Quartier d'Harraud Turrou           +33-5-61-50-97-01 (Fax)
31190 AUTERIVE                      +33-6-07-63-80-64 (GSM)
FRANCE                      Email: ohp@pyrenet.fr
------------------------------------------------------------------------------
Make your life a dream, make your dream a reality. (St Exupery)


Tue, 28 May 2002 14:28:13 +0200 (MET DST)
Olivier PRENANT <ohp@pyrenet.fr>
Re: WAL FILES

8 is the maximum unless WAL files have to be created _while_ the
checkpoint is taking place.

Current CVS SGML has:

   The number of 16MB segment files will always be at least
   <varname>WAL_FILES</varname> + 1, and will normally not exceed
   <varname>WAL_FILES</varname> + MAX(<varname>WAL_FILES</varname>,
   <varname>CHECKPOINT_SEGMENTS</varname>) + 1.

The real driver here is CHECKPOINT_SEGMENTS because WAL_FILES is going
away in 7.3 and will just be dynamically used.  The typical setup is
checkpoint_segments files.  I will also add better reporting so you can
know if your checkpoint_segments is too small, causing checkpoints too
frequently.

---------------------------------------------------------------------------

Olivier PRENANT wrote:
> Hi Bruce,
> 
> Thank you for your reply. It makes a lot of sense!
> However I don't really understand why we can't control the NUMBER of
> files.
> Are the 8 files I see a maximum usage when I reloaded the databases on the
> ne system or is it some sort of "plugged in value"?
> 
> Thank you for your explanation.
> On Mon, 27 May 2002, Bruce Momjian wrote:
> 
> > Date: Mon, 27 May 2002 17:17:58 -0400 (EDT)
> > From: Bruce Momjian <pgman@candle.pha.pa.us>
> > To: ohp@pyrenet.fr
> > Cc: pgsql-hackers list <pgsql-hackers@postgresql.org>
> > Subject: Re: [HACKERS] WAL FILES
> > 
> > Olivier PRENANT wrote:
> > > Hi every one.
> > > 
> > > I just moved (at last!) to 7.2.1. Works like a charm...
> > > I'm suprised though by the number of WAL files.
> > > 
> > > I have 8 files where postgresql.conf says WAL_FILES=4.
> > > 
> > > What did I miss ? (I have no outstanding transaction)
> > > 
> > > FWIW, t's on UW711.
> > 
> > No, you are fine.  The current GUC params are confusing. I did update
> > the documentation for 7.3, but I plan to reorganize those params to be
> > more meaningful.
> > 
> > Actually, I have in TODO:
> > 
> >   Remove wal_files postgresql.conf option because WAL files are now
> >   recycled 
> > 
> > because the param no longer controls what you think it controls.  In 7.1
> > WAL files where not recycled, so WAL_FILES was used to pre-allocate
> > files so there wasn't as much happening during checkpoint.  Now, with
> > recycling, there is no need.
> > 
> > 
> 
> -- 
> Olivier PRENANT         	Tel:	+33-5-61-50-97-00 (Work)
> Quartier d'Harraud Turrou           +33-5-61-50-97-01 (Fax)
> 31190 AUTERIVE                      +33-6-07-63-80-64 (GSM)
> FRANCE                      Email: ohp@pyrenet.fr
> ------------------------------------------------------------------------------
> Make your life a dream, make your dream a reality. (St Exupery)
> 
> 

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026

Tue, 28 May 2002 21:02:08 -0400 (EDT)
Bruce Momjian <pgman@candle.pha.pa.us>
Re: WAL FILES