Analyzing SAP Memory Configuration

TOOLS • ADMINISTRATION • MONITOR • PERFORMANCE • SETTINGS/BUFFER • BuFFER or via Transaction ST02.

Analyzing SAP Buffers

In the BuFFER section of the SAP memory configuration monitor, you will find information on the SAP buffers

Fields in the Memory Configuration Monitor

FieldExplanationHITRATIOHit ratio of the buffer. The definition of the SAP
buffer hit ratio is identical to that given in the
chapter on database buffers.ALLOCATEDMemory space allocated to the respective buffer.
Every SAP buffer is normally characterized by
two parameters: the size of the buffer and the
maximum number of buffered entries.FREE SPACECurrerntly unoccupied memory space in the buffer.DIR. ENTRIESMaximum number of entries in the buffer.FREE DIRECTORY ENTRIESDifference between the current number of objects
stored in the buffer and the maximum possible
number of objects.SWAPSNumber of buffer objects displaced from the
buffer.DATABASE ACCESSESNumber of database accesses (which is also the
number of data transfers from the database into
the buffer).

When monitoring SAP buffers, consider the following guidelines:

->The hit ratio for SAP buffers should generally be 98% or higher. (Exception: For the program buffer, the single-record buffer, and the export/import buffer, lower hit ratios are acceptable.)
->There should be no swaps (displacements) in the buffers of a production system. If there are swaps, the buffer size or the maximum number of entries should be increased. Here again, the exception is the program buffer, for which approximately 10,000 swaps per day represents an acceptable number of buffer displacements .
->To help avoid subsequent displacements, ensure that each buffer has sufficient memory (indicated as FREE SPACE) and free entries (indicated as FREE Dl RECTORY ENTRIES).

If you detect displacements in an SAP buffer, proceed as follows:

1. First check in the memory configuration monitor whether these displacements are due to an excessively small buffer (field: FREE SPACE) or due to an insufficient maximum number of possible buffer entries (field: FREE DIRECTORY ENTRIES).

2. Depending on the results of these checks, increase either the buffer size or the maximum number of allowed entries by 10-50%. To determine the relevant SAP profile parameters, select the CURRENT PARAMETERS function. Before increasing the buffer size, ensure that the computer still has sufficient main memory reserves; otherwise, you run the risk of a memory bottleneck.