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checkpoint segments

From: "David Parker" <dparker(at)tazznetworks(dot)com>
To: <pgsql-performance(at)postgresql(dot)org>
Subject: checkpoint segments
Date: 2005-05-16 00:22:13
Message-ID: 07FDEE0ED7455A48AC42AC2070EDFF7C74609A@corpsrv2.tazznetworks.com (view raw or flat)
Thread:
Lists: pgsql-performance
I was recently running a test with multiple client shell processes
running psql commands (inserts) when all the client processes appeared
to hang simultaneously. I assumed that I had an application deadlock
somewhere, but after a few seconds - less than a minute, but certainly
noticeable - all the clients picked up again and went on their way.
 
In the database log at that time there was a "recycling transaction log"
message which seems to correspond to the time when the clients were
paused, though I don't have it concretely correlated. 
 
I've seen these messages in the log before, and am aware of the need to
increase checkpoint_segments, but I wasn't aware that recycling a
transaction log could be that damaging to performance. There may have
been some local hiccup in this case, but I'm wondering if recycling is
known to be a big hit in general, and if I should strive to tune so that
it never happens (if that's possible)?
 
Thanks.

- DAP
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David Parker    Tazz Networks    (401) 709-5130
 


 

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