This section contains a detailed description of the components of the Java Startup Framework, their interaction and communication, and the architecture of the Java Startup Framework. You can follow the steps when starting, monitoring, or stopping an AS Java instance.
The Java Startup Framework is implemented in the JSTART program.
The JSTART program has two roles:
When running as the Java instance controller, JSTART starts, stops, and monitors the processes of a Java instance (the ICM process and several Java server processes). In this role, JSTART provides a local port for command communication and implements the SAP signal handling to stop the instance.
In the role of a server process, JSTART connects to the Java instance controller before loading the Java VM into its address space. It then starts the AS Java code and represents the Java server process. The program can receive commands from the Java instance controller and reports the status of the Java server to the instance controller. A Java server process stops immediately when it detects that the Java instance controller has terminated unexpectedly.
The Java Startup Framework is called in different ways depending on the operating system and installation type:
In an ABAP+Java instance, the ABAP dispatcher calls the JSTART program.
In a pure AS Java installation, the following distinction applies:
Under Windows, the SAP Start Service calls JSTART to start an AS Java instance.
Under UNIX and OS/400 platforms, the SAP Start Service uses the startsap and stopsap scripts to call the JSTART program.
AS Java Startup Framework (contains general information about the components of the Java startup and control framework)
For more information about the AS Java cluster and system architecture, and about the communication between the AS Java and the other components within the SAP NetWeaver Application Server, see the AS Java Architecture Manual .