![]() ![]() Because it can be very expensive to copy big sessions, there is a limit where copying into the shared pool is stopped (defined by vmcj/property/). When the user sends an other request to a VM, the user session is copied back into the local Java heap. When a VM is put back into the pool the session is stored as a copy only shared closure in the shared pool. SAP note 1020539 – “Memory management in the VM container” for more information on the different areas of the shared pool.Ī user session is a Java object used by the application to store some user specific data. It is separated into different parts for different kinds of objects (Classes, Data, Sessions, compiled programs, Locks. SHARED POOL is used to store shared Java objects (shared closures) which are available for all Java VMs. It has a dynamic size and when it is full a Full Garbage Collector (Full GC) clears it. Old generation, where the objects that have survived two local GCs are moved.When it is full a Local Garbage Collector (Local GC) collects the objects no longer required and release their memory. ![]() ![]() Young generation, where the new objects are created.JAVA HEAP is used for the local Java Objects. VM HEAP which is used for the VM itself to work (local classes, local misc.). This means we should only adjust the size of the shared pool and apply the recommendations in note 1083358 - VMC: Recommendations for parameter settings. Different log files where the information related to VMC is also logged: log files of the work processes (dev_w*), of the dispatcher (dev_disp).Transaction SM52, especially Virtual Machine Container tab of the Menu -> Error Information.There are three types of VM: template, auto java and RFC. Once the Java program has been executed, the VM is detached from the work process (roll-out).Only one VM can be active at one time in a work process. One free VM is attached to the work process (context roll-in) and this remains if at least one active java thread exists.User context is loaded into the work process that is running.From the VMC point of view, a JCO transfers the call with all the parameters and the java classes are loaded. VMC isn’t related to JAVA J2EE Engine.įrom the ABAP point of view, the process is like a normal RFC. The VMC is used as a runtime environment for selected SAP Java components (for example, Internet Pricing Configurator), that are executed on a Java VM integrated in an ABAP work process. Java applications are normally executed on the J2EE Engine. In the VMC is really important to apply the last available path level for the kernel and follow the recommendations given in note 1083358 - VMC: Recommendations for parameter settings. Frequent Shared Garbage Collector (SGC) or SGC time outs.Dumps like VM_STACK_TRACE or RFC_VMC_COMMUNICATION_ERROR. ![]()
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