7.2.2 Stateful session beans
A stateful session bean is used to capture state information that must be shared across multiple consecutive client requests that are part of a logical sequence of operations. The client must obtain an EJB object reference to a stateful session bean to ensure that it is always accessing the same instance of the bean.
WAS supports the clustering of stateful session bean home objects among multiple appservers.
WAS does NOT support the clustering of a specific instance of a stateful session bean. Each instance of a particular stateful session bean can exist in just one appserver and can be accessed only by directing requests to that particular appserver.
State information for a stateful session bean cannot be maintained across multiple cluster members.
Stateful session bean instances cannot participate in WebSphere workload management.
One significant improvement introduced in WAS V6 is the failover support for stateful session beans, which means that the state information maintained by a stateful session bean can survive various types of failures now. This is achieved by utilizing the functions of the Data Replication Service (DRS) and server workload management (WLM). (EJB high availability and failover).
Even though stateful session beans are not workload-managed themselves, a certain level of WLM can be achieved when the homes are evenly distributed. It is only after the bean is created that everything will be performed on the same cluster member.