Remote Objects Garbage Collection 

Use

The SAP J2EE Engine P4 Provider Service provides a reference-counting garbage collection mechanism that automatically removes objects that are not referenced by any clients.

The P4 Provider Service keeps a strong reference to each remote object that has client references to it. This reference is kept as long as there are clients connected to it. Transmitting the object by value increases the count of the remote references to that object. The other way around – if the stub of that object is removed by the garbage collector, or the connection between the client and the server is terminated, where the remote object resides – decreases the count of the remote references to the object. At the moment when the number of clients connected to that object becomes 0, the P4 Provider Service releases the strong reference to that object and keeps only a weak reference to it. This way, the JVM can perform garbage collection for that object, since no local references exist to it.

The terms strong and weak references here are used in the sense of subclasses of the java.lang.ref.Reference class. For more information about the topic, refer to the API documentation of the java.lang.ref package on Sun Microsystems’ website at http://java.sun.com. Do not confuse these terms with the strong and weak references used to define references between the SAP J2EE Engine components as described in the Architecture Manual.