SAP Basis

Unit 1: Fundamentals ADM100
Figure 8: Program Buffer with the Use of Logon Groups
One instance is not included in the logon groups in the figure. This is the
central instance. This arrangement is useful, since it means that end users
cannot log on to the central instance; only the administrators can do this.
In the example shown above, the definition of the two logon groups has
the following effects:
With a logon using a logon group, the SAP Logon program connects to
the message server of the system, and receives from it the name of the
currently best performing instance of the selected logon group. SAP Logon
then starts the SAP GUI program with the connection parameters for the
selected dispatcher.
Within a logon group, end users are, for example, only using a particular
application. In the example, these are the FI and SD applications.
Therefore, the buffers on the instances of each of the logon groups are
filled with contents from these applications. This means that the program
buffer of each of the instances shown contains fewer different programs
than they would without the use of logon groups. This has two possible
advantages as a consequence:
1. The program buffers can be set up more “economically” (smaller).
2. Less “swapping” is performed for the program buffers, and they
therefore perform better.
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