Database persistence using WebSphere Application Server session management

Storing session information in a database, sometimes referred to as persistent sessions or session clustering, is one method to share distributed session information among cluster members. With this option, whenever an application server receives a request associated with a session ID, which is not in memory, it can obtain it by accessing the back-end database, and can then serve the request. When this option is not enabled, and another clustering mechanism is not used, if any load distribution mechanism happens to route an HTTP request to an application server other than the one where the session was originally created, that server would be unable to access the session, and would thus not produce correct results in response to that request. One drawback to the database solution, just as with application data, is that it provides a single point of failure, so it should be implemented in conjunction with hardware clustering products such as IBM HACMP, TSA, or solutions such as database replication. Another drawback is the performance hit, caused by database disk I/O operations and network communications.

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