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Author's profile photo Mauricio Grisa

High swaps in transaction ST02


I work on SAP Product Support. There are a couple of incidents opened by customers related to high swaps in transaction ST02. My goal with this post is to share some information about causes and solutions related to this topic.

In transaction ST02, a few thousand swaps can be tolerated each day. However, you should consider to enlarge the buffer if you find more than 10000 swaps per day. As you can see in ST02 main screen, there are several types of buffer. The most problematic buffers are listed below:

  • Nametab buffers: it is recommended that you check SAP Notes 16244 and 1398802. P.S.: check if you have run SGEN recently. I can tell youit is normal that a lot of nametab entries are required during SGEN.
  • Export/import buffer: importing programs can occupies the buffer (in case you are transporting many requests). It is recommended that you check SAP Notes 702728 and 373986.
  • Program buffer: it is recommended that you check SAP Notes 552778 and 147568.

Additional information about buffers can be found in the following notes:

SAP Note 1918603 – High swaps in transaction ST02

SAP Note 103747: Performance: Parameter recommendations as of Release 4.0

NOTE: It is difficult to say what are the exact values for the parameters of your system. It depends on several factors: number of concurrent users, workload, hardware resources, etc.

Best regards,

Maurício Grisa.

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      Author's profile photo Nilesh Vangujar
      Nilesh Vangujar

      Hello Mauricio Grisa

      Kindly let me know , how to increase size of buffer?



      Author's profile photo Isaias Freitas
      Isaias Freitas

      Hello Nilesh,

      The size of each buffer is determined by a parameter.

      To increase the size of a specific buffer, just increase the value of the parameter.



      Author's profile photo Thomas Michael
      Thomas Michael

      I don't think it's a simple matter of increasing  parameters values to resolve swap issues and other tunes. Here is an example:

      A section of ST02 where Swaps are visible.

      Double-click on the Entry with Swaps to see assigned Space details

      You can see above (A) that there's plenty of Free Space (97MB), and you can see that there are 1853  Free Directory entries. So why are objects being Swapped?

      From the above screen, there's a Button called: "Current Parameters ". If you click on it , you will see and validate the parameters values that control the Swapping Buffer, as we see in the screen below:

      We can see that the Dir. Entry Count is set to 30000 but they aren't only for the Swapping buffer but rather of all the "NameTab" buffers section. The Sawpping Buffer has only 7500 entries available to it.

      But even the 7500 entries aren't all consumed and there's free space yet the Buffer still swaps Objects!

      This seems to indicate that the "swapping" is dynamic and what we see in ST02 are not the final values but rather a snapshot of current situation. May be at some point T, a Work Process tries to buffer something but at T all the Entries were being used but later freed up!

      May be SAP should create Parameters specific to each Buffer rather than to a whole memory section based parameter like the Directory Entries Param that applies to many buffer at once. Or may be I missing something?

      My conclusion is that currently, setting ST02 parameters is more of an art (tuning by trial an error) rather than a science (totally analytical)!

      Have fun!

      Atman Nouiouat.