Message-ID: <48E27617.7020005@otg-nc.com>
Date: Tue, 30 Sep 2008 14:55:19 -0400
From: Chander Ganesan <chander@otg-nc.com>
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To: Tom Lane <tgl@sss.pgh.pa.us>
CC: Jonny <blubb@terminalschmiede.de>, pgsql-admin@postgresql.org
Subject: Re: turning of pg_xlog
References: <48E0B559.3070406@terminalschmiede.de>
	<48E26C60.3060307@otg-nc.com> <23386.1222800278@sss.pgh.pa.us>
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Tom Lane wrote:
> Chander Ganesan <chander@otg-nc.com> writes:
>   
>> You should also understand that if you set checkpoint_segments to a 
>> small number, its still possible that PostgreSQL might use more than 
>> that number for a large transaction.
>>     
>
> "Large transactions" have nothing to do with this.  You are confusing
> Postgres' implementation with Oracle's.
>
> 			regards, tom lane
Okay.  I guess my use of the word "transaction" here was erroneous - 
probably comes from my oracle background :-( .  However, the fact 
remains that its possible to exceed checkpoint_segments in certain 
scenarios (I think the docs refer to it as a peak in log creation or 
something like that), which - if it fills up the disk that the WALs are 
on, can result in issues...  And one should be wary of that when trying 
to limit the number of WALs in order to meet limited disk space 
requirements.

-- 
Chander Ganesan
Open Technology Group, Inc.
One Copley Parkway, Suite 210
Morrisville, NC  27560
919-463-0999/877-258-8987
http://www.otg-nc.com