Memory-to-memory session replication using WebSphere Application Server session management

Memory-to-memory replication enables the sharing of sessions between application servers without using a database. It uses the built-in Data Replication Service (DRS) of WebSphere to replicate session information stored in memory to other members of the cluster.

Using this functionality removes the single point of failure that is present in persistent sessions through a database solution that has not been made highly available using clustering software. The sharing of session state is handled by creating a replication domain and then configuring the Web container to use that replication domain to replicate session state information to the specified number of application servers. The administrator can define how many replicas should exist in the domain (either a single replica, a defined number, or the entire domain).

Memory-to-memory replication also incurs a performance hit, primarily because of the overhead of network communications. Additionally, because copies of the session object reside in application server memory, this reduces the available heap for application requests and usually results in more frequent garbage collection cycles by the application server JVM.

Note: Depending on your application (for example, the session size) and on your hardware resources, memory-to-memory replication or database persistence might be the better solution for your environment. Refer to WebSphere Application Server V6 Scalability and Performance Handbook, SG24-6392, for additional information about resource requirements and performance for either option.

xxxx