Message-ID: <468361A9.1040308@archonet.com>
Date: Thu, 28 Jun 2007 08:22:17 +0100
From: Richard Huxton <dev@archonet.com>
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To: Ho Fat Tsang <namiwf@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: PostgreSQL 8.0 occasionally slow down
References: <97e6e20f0706272354m5e42c91em177c8b80abb2ea52@mail.gmail.com>
In-Reply-To: <97e6e20f0706272354m5e42c91em177c8b80abb2ea52@mail.gmail.com>
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Ho Fat Tsang wrote:
> 
>   I am new for postgresql server. And now i work on a projects which
> requires postgreSQL 8.0 and Java. I don't know why the server occasionally
> slow down a bit for every 3 minutes.

> Do anyone can help me about this ? or any resolution for a sudden
> performance degrade ( because the application i need to develop is quite
> time-critical).

It's probably checkpointing. PG will write updates to the transaction 
log (WAL) immediately and update the main data files later. Every so 
often it makes sure the data files are up-to-date and this is called 
checkpointing.

You want checkpointing to happen more often, not less. That way the load 
will be less each time it happens. See the manual for details.

-- 
   Richard Huxton
   Archonet Ltd