Failover for J2EE Web Applications 

The J2EE Engine provides a high degree of fault tolerance for the J2EE Web applications that are deployed on it, by implementing an effective mechanism for replicating sessions. At the end of each request-response cycle, the HTTP session is replicated to a persistent storage. If the system crashes, the storage is used to retrieve all lost session states. Replication is done using standard Java serialization techniques, which is the only possible way of doing it within a Java Virtual Machine. This technique has certain tradeoffs – performance on one hand, and restrictions to the application on the other. These issues are described in HTTP Sessions and Failover of Web Applications in the Development Manual.

For more information about enabling and configuring the failover services on the J2EE Engine, see the Failover System in the Administration Manual.