Process affinity

Whatever the workload management server selection policy, if an EJB is available in the same cluster member as the client, all the requests coming from the client will be directed to this EJB. This is called process affinity, because all the requests are in-process requests. The advantage of process affinity is that there is no need for serialization for method calls. Parameters can be passed by value without any serialization costs, since all method calls are performed within the same Java virtual machine, in the same memory space.

To take advantage of process affinity, the client can only be a servlet or an EJB. In the case of a servlet, process affinity is only possible if the Web container running the servlet is in the same appserver as the EJB container. In the case of an EJB (a stateless session bean acting as a facade, for instance, as recommended by EJB development best practices), process affinity occurs when the called EJB is in the same EJB container as the calling EJB. With IBM WAS Network Deployment V5.1, you can only have one EJB container per application server.

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