Re: Interpretting WAL debug.

>-----Original Message-----
>From: Marc Mitchell [mailto:marcm@eisolution.com]
>Sent: Thursday, August 29, 2002 16:13
>To: Murthy Kambhampaty
>Subject: Re: [ADMIN] Interpretting WAL debug.
>
>
[snip]
>So, is it fair to assume that you have enough WAL_FILES declared if you
>never receive these messages?  I've observed these in the past but only
>during timing of running Vacuums or restores of entire
>databases.  During
>normal operation I don't think I see these.

Right. Of course the WAL files don't take up too much room on disk,
relatively speaking, so I just set that parameter to the max of 64 (1G) on
all our servers, and then worry about the checkpoint interval.

>
>Marc
>
>> >-----Original Message-----
>> >From: Marc Mitchell [mailto:marcm@eisolution.com]
>> >Sent: Thursday, August 29, 2002 11:13
>> >To: pgsql-admin@postgresql.org
>> >Subject: [ADMIN] Interpretting WAL debug.
>> >
>> >
>> >In an attempt to review a machine for optimal OLTP configuration of
>> >Postgres box, turned WAL debug to 1 and ran under load for 24
>> >hours.  That
>> >resulted in a 67+ meg postmaster logfile.  But I'm not sure how to
>> >interpret the results.  Without going through the 700,000+
>> >lines, the basic
>> >info looks like this:
>> >
>> >
>> >INSERT @ 7/2838581988: prev 7/2838573716; xprev 7/2838573716;
>> >xid 38868268;
>> >bkpb
>> > 1: Btree - insert: node 18720/20077; tid 219/75
>> >INSERT @ 7/2838590260: prev 7/2838581988; xprev 7/2838581988;
>> >xid 38868268;
>> >bkpb
>> > 1: Btree - insert: node 18720/11144803; tid 201/94
>> >INSERT @ 7/2838598532: prev 7/2838590260; xprev 7/2838590260;
>> >xid 38868268:
>> >Heap
>> > - update: node 18720/19299; tid 431/8; new 431/21
>> >XLogFlush: rqst 7/2838540592; wrt 7/2838593536; flsh 7/2838524040
>> >XLogFlush: rqst 7/2838557172; wrt 7/2838598740; flsh 7/2838598740
>> >XLogFlush: rqst 7/2838565444; wrt 7/2838598740; flsh 7/2838598740
>> >XLogFlush: rqst 7/2838573716; wrt 7/2838598740; flsh 7/2838598740
>> >
>> >
>> >I know in general that I'm looking at inserts into the log
>buffers and
>> >flushes of the buffers to permanent storage.  I also know that a bad
>> >situation is one where all buffers fill up and an insert must
>> >wait for a
>> >flush.  How can I examine this output to know if that is
>> >happening?  Also,
>> >is there anything else I can look for within this data to tell
>> >me if I have
>> >a configuration problem that could use some tuning?
>> >
>> >FYI:
>> >                           version
>> >-------------------------------------------------------------
>> > PostgreSQL 7.1.2 on i686-pc-linux-gnu, compiled by GCC 2.96
>> >
>> >
>> >Thanks for any help that can be provided.
>> >
>> >Marc Mitchell - Senior Application Architect
>> >Enterprise Information Solutions, Inc.
>> >Downers Grove, IL 60515
>> >marcm@eisolution.com
>> >
>> >
>> >
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