SAP BASIS Administration Tutorials: Process of a System Logon (ABAP)

Topic Overview :

In this Topic, you will learn about the process of a system logon, and about dialog

work process multiplexing.

Topic Objectives:

After completing this Topic, you will be able to:

• Describe the process of a system log on
• Describe the technology of dialog work process multiplexing

Process of a System Logon (ABAP)

To create a connection between the front end of an end user and an instance of an SAP system, the sapgui.exe program requires various information in the form of start parameters. This parameter string is normally created by the saplogon.exe program using information about the system selected for logon. This information comes partly from the configuration files of SAP Logon, and partly from a direct request to the message server of the selected system (see steps 1 and 2 in the following figure). SAP Logon then starts the SAP GUI with these specifications.

After the transfer of the logon screen from the dispatcher to the front end (not shown in the figure), SAP GUI sends the user's logon data to the instance (step 3 in the figure). After the dispatcher has determined a free work process to process the logon, it transfers the logon data to this work process (step 4). The work process, in turn, checks whether the received combination of user ID and password is known to the system using a request to the database (steps 5-8). A positive response from the database prompts the work process to return the initial screen of the system to the front end.

During a logon session, the assignment of the user to the instance is unique. Only during a new logon can the user possibly be assigned to a different instance by the

message server.

Dialog Work Process Multiplexing

The processing of a transaction that consists of multiple screens is usually executed using multiple, different dialog work processes. This distribution is called work process multiplexing. Work process multiplexing means that a system function whose content is logically connected but consists of multiple substeps can be processed by various dialog work processes. These steps, where the content is connected, are described as transactions. A transaction that consists of multiple screens, such as screens 100 and 200 can also be processed by multiple dialog work processes.

The figure shows two screens of a transaction (100 and 200), for which the input is handled by two different dialog work processes. The multiplexing procedure is used exclusively for dialog work processes. All other work process types process entire functions; that is, complete business processes. As dialog work processes may therefore process only parts of transactions that are connected from a business point of view; the update procedure with the update work process is widely used in SAP systems.