Data Buffer Quality increase in ST04

[Former Member]

Hi Experts,

What are the ways to increase data buffer

Quality percentage

in ST04.In my sap production systems

shows 92.3%. I would like increse as 97%.

can any one suggest any sap note or Document?

Thanks in advance

sundar.c

[fidel_vales · Accepted solution]

Hi,

It is a (very) bad idea only to tune an Oracle system based only on the Data Buffer Quality.

It is a prehistoric tuning method that should not be used any more.

You should check were the DB time is being spent and try to tackle it.

Use the Wait Event Interface for tuning.

If you want some notes, start here:

SAP Note 619188 FAQ: Oracle wait events

SAP Note 766349 FAQ: Oracle SQL optimization

SAP Note 767414 FAQ: Oracle latches

But before, you should read the oracle documentation. Starting on the [Concepts|http://download.oracle.com/docs/cd/B19306_01/server.102/b14220/toc.htm] and then the [Performance Tuning Guide|http://download.oracle.com/docs/cd/B19306_01/server.102/b14211/toc.htm]

[Former Member]

hi,

be carefull when tuning this parameter. data buffer quality for sap server is good category when ranging on 90% to 95% (i read from SAP Performance Optimization Guide from SAP Press). from your information, your server performance is on good performance.

you cannot rely just on your ST04 information. and read relevant sap notes if you still want to increase your data buffer quality.

best regards,

ardhian

[lbreddemann]

from your information, your server performance is on good performance.

And this is exactly the kind of information that cannot be read from a number like buffer cache hit ratio.

There's simply no way to figure out wether a system is running fine or terribly bad by reading this number.

you cannot rely just on your ST04 information. and read relevant sap notes if you still want to increase your data buffer quality.

In fact, you can easily increase the Buffer Quality yourself: read more data from the buffer!

Drop some indexes that you use very often and where the table is likely to fit into your buffer et voilá: the buffer quality increases!

Of course there are now ridiculous numbers of blocks to be read from the cache - but they are read from the cache.

So, no better performance here - but much better BCHR.

Please, just forget about this number - it does not tell you anything.

Regards,

Lars

[Former Member]

Is it the normal trend in st04 ?

Normally after a DB restrart the database buffers shows low buffers quality.You should wait few days to see the real buffers quality.

In my point of view if the quality does not improve even after 30 days.

Try to increase the number of buffers or parameter DB_CACHE_SIZE

hope it helps.

Amit