ST02

My reference: https://itsiti.com/st02-tune-summary

ST02: Tune Summary

Transaction code ST02 is used to display the current status of  memory resource usage for a specific SAP application server.

1. The hit ratio for the R/3 buffers should be 98% or better. Hit ratio less than 98% can be regarded as acceptable only for the Program buffer, the single record buffer and export/import buffer. There should be no swaps in the buffers. If there are swaps the buffer size or the max. numbers of entries should be increased.(appr. 10000 swaps per day represents an acceptable number of buffer displacements)

Hint:
• HitRatio – The percentage of data accesses that are satisfied by the buffer and do not require database accesses. HitRatio for each buffer > 98%.
• Check the free space & the free directory for each buffer.
• Check Hits, program buffers should be 10000 hits/day & for other buffers it should be 1000 hits/day.

Solution:
• Amend the Buffer parameter values by increasing the old value by adding approx 10% and then restart the system. Buffer swapping is normal as long as the HitRatio > 98% , then nothing need to be change.

2. If R/3 extended memory is full (when max.used > 80% in memory) -> Go to Detail analysis menu -> SAP memory -> Mode list Individual users consuming a lot of memory -> Analyze user actions. Enlarge the R/3 extended memory if there is enough main memory. Hint: Current usage of Extended memory < 80%.

3. Hint: Hit ratio > 95% for “Select” and “Select Single”.

Additional note:
• Hitratio : The percentage of data accesses that are satisfied by the buffer  and do not require database accesses.

• Allocated : Max. amount of memory area that can be occupied by the respective buffer as defined by the parameter limiting the buffer size.

• Free Space : Currently unoccupied memory space in the respective buffer.

• Dir. Size Entries : Max. number of objects that can be stored in the buffer.

• Swaps : Number of buffer objects displaced from the buffer.

• Database access : Number of database access. (data transfers from the database into the buffer)

• Free Directory Entries : Difference between the current number of objectsstored in the buffer and the max. possible number of objectes.