VM Container Functions (Menu VMC) 
The VMC menu in the overview screen of the transaction provides the following administration functions for the VM container:
Display and change the VMC status
Details of sessions and opened files; detailed error information
Activate/deactivate startup debugging
A confirmation popup appears before most functions are executed.
Prerequisites
The VM Container is active and you are on the initial screen of the VM Overview (transaction SM52).
Features
The Virtual Machine Container menu provides the following functions:
Display Status
Activate
Deactivate
Reset
Check VM Pool
Memory
Sessions
Files
Error Text
VM Reservation
Debugging
Shared Lock Statistics
Exit
Display Status
Choose 
VMC 
Display Status 
to display the value of the VMC status variables. This displays information about the VMC, which you can also see in the header area of the initial screen (see VM Overview: General Information). You can also see information about the SAP kernel, and about the activation status of startup debugging (see below).
Activate
Choose VMC Activate to activate the VM Container to enable interprocess communication with the ABAP processor. If necessary, the system starts non-instantiated VMs in accordance with the server configuration.
Deactivate
Choose VMC Deactivate to deactivate the VM Container so that inter-process communication with the ABAP processor is no longer possible. VMs already instantiated will continue to run.
Caution
If the VM container is deactivated, any ABAP programs using the VMC functions are terminated by a short dump.
Reset
Choose VMC Reset to initialize the VM Container again.
Caution
When the VMC is reset, all open user sessions using the VMC are deleted. So only use this function in exceptional circumstances, or if you are sure that there are no active users on the server.
Check VM Pool
Choose VMC Check VM Pool , to examine the VM pool. The check specifies whether the current number of VMs lies within the defined area [minimum number of VMs, maximum number of VMs]. If it does not, VMs are either started or also stopped.
Memory
Choose VMC Memory Check to check whether VM memory areas in the shared memory are still occupied, even though the associated VM is no longer running. If there are no memory areas still occupied, you will get the message Memory Areas OK. If memory areas are still occupied, you will get the message Unreferenced memory areas found. Choose VMC Memory Cleanup . The memory areas still there are then deleted.
Trigger Shared Garbage Collection
You can trigger a shared garbage collection by choosing VMC Memory Shared GC . You can reset the counter for the shared GCs by choosing VMC Memory Delete GC Counter .
More information: How the Shared Garbage Collector Works.
Sessions
Choose VMC Sessions Display to see in the VMC Sessions view the number and attributes of the user sessions currently running. The maximum number of sessions configured is also given in the header line.
Choose VMC Sessions Check to start the check in the VMC session table. In this table all the valid Java sessions of the Virtual Machine Container (VMC) are managed. It consists of a kernel and a Java part. The check examines the consistency of both parts. You can run also this check periodically by setting the parameter rdisp/sessionTableCheck (see Configuration Parameters).
Files
Choose VMC Files to display in the VMC Files view the number and attributes of the files currently opened by the VMC. The maximum number of files configured is also given in the header line.
Error Text
Choose VMC Error Info to get details of the last error that occurred (see VM Overview: General Information).
VM Reservation
Choose VMC VM Reservation to temporarily reserve a VM of type RFC, for example, to set specific trace flags in this VM.You can reserve the VM using the submenu Activate. The VM will then be flagged in the Table of VMs with the reserved status and with your user name. Choose VMC VM Reservation Deactivate to cancel the reservation.
Debugging
You can make the following configuration settings for the debugging.
Startup debugging enables debugging when the VM is initialized.
The debug proxy is used for accelerating Java debugging via WAN.
Startup Debugging
This function sets up the connection to a debugger when a VM is initialized, which is at the earliest possible time. A confirmation popup appears.
Switch on
Choose VMC Startup Debugging Activate , so that the system waits for the connection to a debugger for each instantiation of the selected VM type. On the VMC Status screen (see above) the status displayed is Startup debugging is active.
Switch off
Choose VMC Startup Debugging Deactivate , so that the system does not wait for a connection to a debugger for each VM instantiation. On the above VMC Status screen the status displayed is Startup debugging is not active.
Debug Proxy
The debug proxy is a software component that speeds up Java debugging across the WAN. It consists of a back end in the VM container (AS ABAP) and a front end integrated in the SAP NetWeaver Developer Studio.
Note
The debug proxy improves debugging performance, in particular single step debugging in Java applications. Since this does not increase the speed at which variables are read, SAP recommends that you activate this in the Developer Studio only when it is needed.
Start Debug Proxy
If you want to use the debug proxy, you have to start the back end. In the VM Overview (SM52) choose VMC Debugging Debug Proxy Activate .
Check Status
You can check whether the debug proxy is active. In the VM overview (SM52) choose (SM52) VMC Display Status .
Configure Port
The back end of the debug proxy communicates with the front end through a configurable port. The standard setting is 55555, and you can change the port in profile parameter vmcj/debug_proxy/port in the VM container. The parameter can also be changed dynamically in transaction RZ11 when the VM container is running.
As well as this port number, the communication between the VM container (on which the Java application to be debugged is running) and the SAP NetWeaver Developer Studio also requires the debug port of the Java VM. We can see this in the VM overview (SM52) in column Debug Port, as soon as the Java code is debugged. At the same time you are also informed of the port in a popup or in the status bar. You then need to set this manually in the SAP NetWeaver Developer Studio.
Example
If the back end of the debug proxy is running on host PWDF2505 an is communicating via the standard port 55555, and you are assigned port 8000 as the debug port for the VM, you must enter this in the Developer Studio.
Stop Debug Proxy
To stop the debug proxy, choose VMC Debugging Debug Proxy Deactivate .
Shared Lock Statistics
The shared lock statistics produces the following information about Shared Locks:
Lock name: The name of the lock provides information about the application that has set the lock.
Locks: Number of lock operations for a shared lock
Wait time: Total wait time for a shared lock in microseconds
Lock time: Total duration of lock (time in critical section) of a shared lock in microseconds
Minimal and maximal time in the critical section (in microseconds)
Number of lock operations in a specific time interval: In these columns you can see how many lock operations have lasted less than one microsecond, between one and two microseconds and so on.
Choose Shared Lock Statistics Activate to activate the recording of the statistics for the shared lock operations. If the statistics are active, you can display them with Shared Lock Statistics Activate .
You can close the recording (Deactivate) or reset the collected data (Reset).
Exit
Choose VMC Exit to leave the transaction.
Note
This only stops the transaction, it does not stop the VM Container.