Transaction ST02

The buffer tune summary transaction displays the R/3 buffer performance statistics. It is used to tune buffer parameters of R/3 and, to a lesser degree, the R/3 database and operating system.

The buffer is important because significant buffer swapping reduces performance. Look under Swaps for red entries. Regularly check these entries to establish trends and get a feel of the buffer behavior.

1.      In the Command field, enter transaction ST02 and choose Enter (or choose ToolsàAdministration, then MonitoràPerformance, and then Setup/BuffersàBuffers).

2.      The two important things to review are:

§  Hit Ratio, for which the target value is 95 percent and higher

Soon after starting the system, this value is typically low, because certain buffers are empty.  The hit ratio will increase as the system is used and the buffers are loaded. It usually takes a day to load the buffers that are normally used.

§  Swaps, for which the target value is less than 1,000

Swaps occur when the necessary data is not in the buffer. The system has to retrieve the data from the database. The swap value is reset to zero (0) when the system is restarted.

·         Buffer swaps may be due to:

¨      Buffer too small, out of space

¨      Out of buffer directory entries

¨      Fragmentation in buffer, particularly the program buffer

Ø  If program buffer exceeds 10,000, it should be investigated

¨      Generic table buffer

Ø  Sometimes very large buffered objects should be unbuffered (over 2MB)