Architecture of the VM Container 

Die VM Container technology enables a Java VM to be integrated in the ABAP work process (see Architecture of the SAP NetWeaver Application Server, section Technical Components).

In general Java applications are executed on the J2EE Engine (see Java Technology in the SAP NW Application Server). The execution of applications on the Java VM integrated in the ABAP work process is only intended for components developed by SAP.

The VM container technology in connection with a Java VM integrated in the ABAP work process provides the following advantages:

●     Reliability and maintainability as in the ABAP environment

The integration of the Java VM into the ABAP work process enables strict isolation between active user sessions, which guarantees a large degree of robustness and maintainability.

One work process can only process one user request at a time, which means that even if one entire Java VM crashes, only the one user active at this time is affected.

●     Close ABAP/Java communication (in-process)

Since the ABAP and Java VMs run in the same work process, a quick and efficient communication path can be implemented between the two languages, which means that the security and speed of the communications is significantly increased. For further information, refer to the SAP JCo and Container documentation.

●     Administration and Sharing of Resources

While a request is being processed a Java VM works exclusively for one user.There is a pool of VMs dynamically assigned to the work processes. These VMs can access shared data in the shared memory.

○     Java shared closures

Java objects can be moved across process boundaries and shared by processes.  This enables an efficient session failover to be implemented. At the same time shared closures offer the option of reducing the memory consumption of the entire system through process-wide caching.

○     Shared class pool

Java classes only have to be loaded into the memory once, the same as for ABAP PXA, and they can be used by all the processes in the system. This reduces the memory consumption and the start time of further processes.

You can find further information in the following sections:

Sharing Concepts in the VM Container

Resource Management in the VM Container  

Memory Management in the VM Container

●     High Supportability

Since SAP kernel technology is reusable, the monitoring functions of the CCMS can be used. For the reason, the familiar SAP statistics can also be used (see Statistics in the VM Container).

●     Debugging

Each user can dynamically switch to and fro between normal operation and debugging.