ST02 Hitratio

[Former Member]

Hi all

I am learning SAP.

I have a doubt in ST02, I read that, If Hitratio is lessthan 95% it indicates a problem.

I have no information about What is the problem, and how can we solve it?

Plz suggest me this regarding.

Thank you

[former_member618758 · Accepted solution]

Hi Kalyan,

The quality of a buffer and how often it is accessed is measured by the %Hit Ratio. This value will indicate if the information stored in the buffers, such as table entries, programs and screens, is being hit directly from the buffer itself or, on the other hand, if the system needs to bring that data from the database since it was not found in the buffer.

The %Hit Ratio can have several values. For instance, when you start the system the %Hit Ratio will be below the recommended value until you have some activity in the system and the buffer starts to fill up with data. A good performing buffer will have a %Hit Ratio of 95% and above (99%-100% is excellent). Keep in mind though that a value lower to 95% not always shows that you have a problem. This can lead you to pinpoint and start performing an analysis. However, other factors can also affect buffer quality decreasing %Hit Ratio values.

If you check sdn blogs has a very good artical detailing about st02/st03. here is the link:

/people/federico.babelis2/blog/2006/04/19/the-journey-to-tuning-netweaver-components--trip-i-the-basics

Hope this will help,

George

[Former Member · Accepted solution]

Hi ..

When ever u start SAP, the hitratio will be less that 90% but after some time the hitratio will increase gradually,

The data from Datafiles is never fetched Directly, it gets the data and keeps it in the Buffer Cache , and then its read ... when ever an SQL query is passed, if the information is not in the Buffer Cache its a Miss, and if it can get u the info from the Database Buffer Cache, its a Hit.. so there by the HitRatio will fluctuate.

Hope this gives u Insight.

Regards,

Ershad Ahmed

[Former Member]

Hi

When you enter a data say SM50 for the first time after the installation of SAP , 1.This particular data gets converted into SAP undertsandable format by DIAG protocol.

2. Then it passes to dispatcher.

3.Then dispatcher allocates a dialog work process to carry out the request to pull the SM50 screen to your system.

4. Every screen in SAP has a system number.So this dialog work process pulls the screen through message server and searches in the database for sm50 screen and follows the same path to return it on your terminal.

5. This process is recorded in a temporary memory called buffer.

6. Next time when u type in sm50, it passes to diag, dispatcher and dialog work process, but after that instead of seacrhing in the database for huge number of screens it can pull up from the buffer itself. So time for data retrieval is saved.

Hit ratio is the ratio of data retrieval from the buffer and db.So its always better we get data from buffer.so, 95% is the better value for a good performing system.

-Subbu

[Former Member]

Hi

When you enter a data say SM50 for the first time after the installation of SAP , 1.This particular data gets converted into SAP undertsandable format by DIAG protocol.

2. Then it passes to dispatcher.

3.Then dispatcher allocates a dialog work process to carry out the request to pull the SM50 screen to your system.

4. Every screen in SAP has a system number.So this dialog work process pulls the screen through message server and searches in the database for sm50 screen and follows the same path to return it on your terminal.

5. This process is recorded in a temporary memory called buffer.

6. Next time when u type in sm50, it passes to diag, dispatcher and dialog work process, but after that instead of seacrhing in the database for huge number of screens it can pull up from the buffer itself. So time for data retrieval is saved.

Hit ratio is the ratio of data retrieval from the buffer and db.So its always better we get data from buffer.so, 95% is the better value for a good performing system.

-Subbu

[former_member204746]

it is not necessarily a problem:

this number is normally low in the first minutes (or few hours if system if not used) because you have to fill SAP buffers with data.