Checkpoint Frequency to high

craig patton

Checkpoint Frequency to high
Chris,

First, 400 checkpoints per hour is extremely high! Definitely raise your
LOGLOAD parameter so that you take about 4 checkpoints per hour. Keep in
mind that while DB2 is taking a checkpoint, NO OTHER ACTIVITY can take
place. Checkpoints are very short in duration, but at 400 per hour, your
system is quite degraded as you are performing 1 checkpoint about every 9
seconds....Are you positive about the 400 per hour or is that for the whole
reporting period?? 400 is about right for a 24 hour time frame. If it
really is 400/hour, I would take that LOAGLOAD And increase it to 500,000
and then check your checkpoint frequency and adjust from there.

HTH,
Craig Patton
DB2 DBA
Patton Research Group, Inc.


>From: "Hayes, Chris" <[login to unmask email]>
>Reply-To: DB2 Data Base Discussion List <[login to unmask email]>
>To: [login to unmask email]
>Date: Tue, 21 Dec 1999 11:04:55 -0500
>
>While looking through some reports, I noticed that one of our production
>DB2
>subsystems is checkpointing over 400 times an hour during certain times. I
>checked our checkpoint frequency parameter and it is set at 50,000. IBM
>recommends using 25,000 to 500,000 in their Installation Guide. Am I
>correct in thinking that 400 times an hour is excessive? Should I be
>concerned about raising the threshold? IBM's Installation Guide mentions
>that start-up time may be excessive (over 30 minutes) if you specify a
>value
>over 300,000 and you terminate DB2 without a quiesce. Is this a real
>concern or should DB2 always be stopped with a quiesce?
>
>
>
>
>

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Chris Hayes

Re: Checkpoint Frequency to high
(in response to craig patton)
Craig - Thanks for your prompt response.

The report tool I am using breaks up various system statistics by the hour.
The checkpoint frequency numbers range between 0 and 561 (the latest high
water mark) with the highest occurring between 22:00 and 01:00 when we do a
lot of batch updates. Most of the time, the number is under 10 per hour. I
will talk with the system's people about raising this parameter.

Another question occurred to me during this analysis. When DB2 writes the
updated pages during a checkpoint, do these pages remain in the buffer?

-----Original Message-----
From: craig patton [mailto:[login to unmask email]
Sent: Tuesday, December 21, 1999 11:39 AM
To: [login to unmask email]
Subject: Re: Checkpoint Frequency to high


Chris,

First, 400 checkpoints per hour is extremely high! Definitely raise your
LOGLOAD parameter so that you take about 4 checkpoints per hour. Keep in
mind that while DB2 is taking a checkpoint, NO OTHER ACTIVITY can take
place. Checkpoints are very short in duration, but at 400 per hour, your
system is quite degraded as you are performing 1 checkpoint about every 9
seconds....Are you positive about the 400 per hour or is that for the whole
reporting period?? 400 is about right for a 24 hour time frame. If it
really is 400/hour, I would take that LOAGLOAD And increase it to 500,000
and then check your checkpoint frequency and adjust from there.

HTH,
Craig Patton
DB2 DBA
Patton Research Group, Inc.


>From: "Hayes, Chris" <[login to unmask email]>
>Reply-To: DB2 Data Base Discussion List <[login to unmask email]>
>To: [login to unmask email]
>Date: Tue, 21 Dec 1999 11:04:55 -0500
>
>While looking through some reports, I noticed that one of our production
>DB2
>subsystems is checkpointing over 400 times an hour during certain times. I
>checked our checkpoint frequency parameter and it is set at 50,000. IBM
>recommends using 25,000 to 500,000 in their Installation Guide. Am I
>correct in thinking that 400 times an hour is excessive? Should I be
>concerned about raising the threshold? IBM's Installation Guide mentions
>that start-up time may be excessive (over 30 minutes) if you specify a
>value
>over 300,000 and you terminate DB2 without a quiesce. Is this a real
>concern or should DB2 always be stopped with a quiesce?
>
>
>
>
>

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