Date: Fri, 5 Sep 2008 12:24:46 -0400
From: Alvaro Herrera <alvherre@commandprompt.com>
To: Duan Ligong <duanlg@nec-as.nec.com.cn>
Cc: Greg Smith <gsmith@gregsmith.com>, pgsql-performance@postgresql.org
Subject: Re: too many clog files
Message-ID: <20080905162446.GF4353@alvh.no-ip.org>
References: <20080902091602.CA09.DUANLG@nec-as.nec.com.cn>
	<Pine.GSO.4.64.0809020117030.6014@westnet.com>
	<20080905095051.93A6.DUANLG@nec-as.nec.com.cn>
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Duan Ligong wrote:

> Greg wrote:
> > On Tue, 2 Sep 2008, Duan Ligong wrote:
> > > - Does Vacuum delete the old clog files?
> > 
> > Yes, if those transactions are all done.  One possibility here is that 
> > you've got some really long-running transaction floating around that is 
> > keeping normal clog cleanup from happening.  Take a look at the output 
> > from "select * from pg_stat_activity" and see if there are any really old 
> > transactions floating around.
> 
> Well, we could not wait so long and just moved the old clog files.
> The postgresql system is running well.

Move the old clog files back where they were, and run VACUUM FREEZE in
all your databases.  That should clean up all the old pg_clog files, if
you're really that desperate.  This is not something that I'd recommend
doing on a periodic basis ...

-- 
Alvaro Herrera                                http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.