LiveCache Log partition

[former_member199694]

hi,

We have recently started upgrading our systems to LiveCache 7.9.08.16. I am thinking of introducing Log partition to speed up the log writing to log-area.

I think, this would help to avoid Log-queue overflow in case of high load. Wondering, if this feature would help any other way to justify making changes.

Will it any way help reduce the batch-job run time window in normal load?

Would appreciate for any additional information on log partitioning.

Thanks,

Raj

[former_member199694 · Accepted solution]

I would check with SAP Support experts. Thanks for all your contributions though.

Best Regards,

Raj

[Former Member]

HI Ray,

before you think about Log Partitions I would first check if the bottleneck of the Batch job runtime is really the fact that log inforamtion cannot be written fast engough to the log volume when the transaction is committed. You know that Log is written ansynchronously from the LOG IO Querue to the log volume. The application generally has not to wait until the Log page is written to the log volume. Only if the transaction is committed. Then this commit has to be written as fast as possible to the Log volume and the transaction has to wait until the IO has been done.

This analysis has to be done by SAP liveCache Experts. You could open a customer ticket to get more detailed information about the bottleneck.

Regards, Christiane

[former_member199694]

Hi Christiane,

my thinking is implementing new feature log-partition config is the way to go,(whether single log-writer is enough or not) as it would provide scalable config. by additional log-partition as load goes up in future. This is may not be possible with one log-writer config. Any thoughts on this?

Thanks,

Raj

[Former Member]

Hi Raj,

can you tell me the size of your LOG Queue(s). What is the parameter setting of MaxCPUs, and USeableCPUs?

How many LOG Queue overflows do you have? Do you have them regularly?

Did you check the IO write time of your system.

This I would check first before reconfiguring the Log into partitions.

Regards, Christiane

[former_member188883]

Hi Raj,

Please find extract from SAP Note 869267 - FAQ: SAP MaxDB log area

51. How many log partitions can I configure and what effects will this have?

             To speed up writing log entries from the log IO queue to the log volumes, SAP MaxDB provides the option of configuring multiple log partitions as of Version 7.8. This splits the configured log area into several partitions.

A log partition can consist of one or several log volumes.

The sizes of the partitions can be different, in the same way as the sizes of the volumes of the partitions can be different.

Use the database parameter MaxLogWriterTasks to configure the log partitions.

You may read through this note to have more useful information on MaxDB log area.

Hope this helps.

Regards,

Deepak Kori