SAP Performance Analysis with Tcode ST02

2. Explanation on SAP ST02 screens

2.1. SAP Buffer and Memory overview/summary screen
ST02 overview screen show information at instance level and has several sections:

  • Top shows instance name, instance startup date and snap-shot of date time.
  • Buffer section shows different SAP buffer configuration and current status.
  • SAP Memory section shows SAP memory configuration and current status.
  • Call Statistics shows database access information.

I have not encountered a performance case which I need “Call Statistics” data to do analysis, It looks like straightforward. From performance point view, buffer sections and SAP memory section is more critical – that is what I am going to cover in following sections.

2.1.1. SAP Buffer section explanation
Column field explanation

Screen Field Explanation
Buffer Type of buffer like nametab, Program etc.
Hitratio % Namely buffer quality =( total access – physical access)/ total access x 100%.
Alloc. KB Configured or allocated memory space for the buffer type in question.
Freesp. KB Free space = allocated memory space – occupied memory space.
Dir. Size Maximum number of buffer object that can be kept in the related buffer.
FreeDirEnt Free Directory Entry = Directory Size – used Dir Entry.
% Free Dir = free Directory / Dir. Size X 100%.
Swap Number of buffered objects which has been swapped to page area.
DB Access Number of data transfers from the data base to the related buffer.

2.1.2. SAP Memory section explanation
This section shows configured memory/virtual memory for a list of sap memory type and their memory usage.

Column Explanation
Sap Memory Show type of SAP memory
Curr. Use % = allocated memory/total-memory X 100% for the type of memory in question
CurrUS[KB] Currently used memory at the instance
MaxUse[KB] High-water mark since the SAP instance is started
In Mem[KB] Configured total memory
OnDisk[KB] Configured disc space(Virtual memory),only eligible for Page memory and roll memory.
SAPCurCache SAP Cursor Cache
HitRatio Applicable for ID and statement Caches.

2.2. SAP Memory Quotas screen

Column Explanation
texts Sap tasks type like dialog, background etc.
Step Sequence allocation – next memory area only if memory allocated in previous steps is not enough.
Memory type 3 possible memory types under current SAP design: Roll, Extended and Heap
Amount Configured the memory size for the tasks.

The SAP screen quotas screen (see figure 2) answers the question of what is maximum memory a SAP process can use:

  • Dialog tasks can use memory up to an amount <=Roll + Extended + Roll + Heap. Transaction executed online by SAP user is a dialog tasks.
  • Non-dialog tasks can use memory up to an amount <=Roll + Heap + Extended. SM37 background job is a non-dialog task.

Dialog tasks are executed in SAP Dialog work process. RFC calls and online transactions are executed in dialog work processes. Job, update and spool are non-dialog tasks. Jobs are executed “BGD” SAP work processes. Update tasks are executed in SAP “UPD” work processes. SAP transaction SM50/SM66 is a work process monitor.

2.3 SAP mode list screen
Figure 3 screen shows SAP Memory usage for every external session by every logon user who is in the instance.

Column Explanation
user Sap user –same user might have more than one entries
EM used Extended Memory used by a user session in KB
Heap Heap memory used by a user session in KB
Other columns like “I-mode G1″ etc I have not found the need to use those columns for SAP memory analysis.

Mode list has two sections – the upper section show current status, the lower section shows history information.


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