Writing Savepoint blocks db while reading

[Former Member]

Hi,

we installed maxDB 7.7 (community licence). (CPU 8, Cache 16 GB)

When we have a heavy load, every 10 Minutes the database have a really BAD read/write rate - plus collision rates on Data-Segments > 10%.

It lasts about 5-6 minutes.

I can check it with analyzer and knldiag-log, that writing the savepoint takes about 5 minutes (and starts every 600 seconds).

Now my ideas:

Reduce the max_cpus-parameter => reduce the collision rates

But what can I do to reduce the blocking time during writing the savepoint?

Any ideas and parameters?

Thanxs a lot.

regards

Wolfgang

[markus_doehr2 · Accepted solution]

> When we have a heavy load, every 10 Minutes the database have a really BAD read/write rate - plus collision rates on Data-Segments > 10%.

> It lasts about 5-6 minutes.

> I can check it with analyzer and knldiag-log, that writing the savepoint takes about 5 minutes (and starts every 600 seconds).

> But what can I do to reduce the blocking time during writing the savepoint?

How many volumes do you have?

Markus

[Former Member · Accepted solution]

Hi,

it's a Windows 2003 64 bit Server.

About 30 Volumes each with 20 GB.

Datafiles are saved in a SAN-Array.

Regards

Wolfgang

[markus_doehr2 · Accepted solution]

> it's a Windows 2003 64 bit Server.

> About 30 Volumes each with 20 GB.

> Datafiles are saved in a SAN-Array.

Ok.

It seems that your disks are "too slow" for the type of load you have.

You may try to play with the parameter "MaxSavepointTimeInterval" and decrase it, this will increase I/O because more savepoints are written but the delays should be much shorter.

I'd also enable the I/O time measuring so you see what I/O times you have on your disks (x_cons <NAME> time enable). The database analyzer will then tell you the I/O times.

Markus

[Former Member · Accepted solution]

Thanx a lot.

Is it correct to decrease max_cpus to reduce the collision rate while writing Datafiles?

regards

Wolfgang

[former_member229109 · Accepted solution]

Hello Wolfgang,

-> Are you using the latest released version?

What version of the database you have? < patch? Build?>

Post output of the command:

xinstinfo <DB-name>

Please run during the high loading the following command:

x_cons <DB-name> show active 10 10

to see the status of active tasks.

-> u201Cto reduce the collision rate while writing Datafilesu201D

Please collect more information using x_cons database tool and DB Analyzer.

If you have warning from DB analyzer on high collision on region, let us know what region & how high is collision rate.

See more details at:

http://wiki.sdn.sap.com/wiki/display/MaxDB/SAPMaxDBRegions

-> click on 'SAP maxDB Regionsu2019 with the first letter of the region and review more details in this docu.

-> Please review the discussion in the thread:

Thank you & best regards, Natalia Khlopina