Log Buffer

[Colin Dawson]

This has been asked before on CDI but no real explanation was given.

I have the following in the online.log:-

Checkpoint log record may not fit into the logical log buffer.
Recommended minimum value for LOGBUFF is 34.

So.... Can someone explain why and when this message is issued. In the past I've increased the value but I still receive a message to say the "Recommended minimum value" is two bytes greater than the LOGBUFF.

Regards

Colin

There are 10 types of people in the world, those that understand binary and those that don't

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[Gustavo Castro]

The checkpoint logical log record contains information about every
active transaction in the system at checkpoint time. The more active txs
you have the bigger the ckpt record

If the log record does not fit the log buffer, IDS cannot write it to
disk and an error and crash will happen to protect the integrity.

The warning is showed when the number of userthreads grows to the
dangerous limit (The fact that you have 1000 users does not necesarily
mean you will have 1000 active transaction, however the potential danger
exists).

To get rid of the problem your log buffer should be sized properly, the
proper size probably changes from version to version but a rough good
value should be:

40 + 24x[Max Number of userthreads]

this amount is in bytes.

For log buff of 32 KB this should give a max of 1300 userthreads...
what is your number of threads and log buf size?

Anyway I guess a log buffer of 32 KB for a 1500 user instance is too small.

Gustavo

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[Colin Dawson]

I had the error with a 32Kb buffer so I doubled it to 64Kb and still got the error.

I regularly have 2400-2500 sessions connected to the DB so based on the formula you give the log buffer needs to be 40+24*2500/1024=58.6328125. Theoretically a 64Kb buffer should be ok.

Regards

Colin

There are 10 types of people in the world, those that understand binary and those that don't

> Date: Wed, 9 Jan 2008 10:00:09 -0500
> From: gcas...@bellsouth.net
> To: cjd_...@hotmail.com
> CC: inform...@iiug.org
> Subject: Re: Log Buffer

[Gustavo Castro]

The formula is just an approximation, you are very close of the edge,
maybe you had a connection spike.