JControl and JLaunch

JControl – Java Instance Controller

JControl: A native program that starts, stops, and monitors the processes of a Java instance (usually a dispatcher and several server processes). The program implements the SAP signal handling to stop the instance. JControl starts the JLaunch processes.

JControl controls J2EE processes …

JControl is the master process of all J2EE worker processes

Controls the lifecycle of the J2EE instance

Restart of crashed processed

Termination of hanging processes

Sends shutdown signal to instance processes

responsible for starting the processes in the right order (bootstrapping..)

integration of different processes into one J2EE instance (SDM, ICM, ...)

provides the monitoring information in a shared memory segment

supports SAP profiles to share configurations with the ABAP Stack

JLaunch – Java Program Launcher

JLaunch has following tasks:

Read the properties of the program to host

Read the VM properties from the database during startup process

Attach to the administration shared memory segment

Load the shared library of the Java VM

JLaunch starts a Java program. It loads the JVM into its own address space and then represents the required cluster element. The program can receive from notification from the JControl process via named pipes to stop the cluster element, and terminates, if the JControl stops running (fork emulation under Windows).