Session state
Unless you have only a single appserver or your application is completely stateless, maintaining state between HTTP client requests will also play a factor in determining your configuration. In WebSphere V5.1 there are two methods for sharing of sessions between multiple application server processes (cluster members).
- Persist the session to a database
- Memory-to-memory session replication
The memory-to-memory replication (sometimes also referred to as "in-memory replication") eliminates a single point of failure found in the session database (if the database itself has not been made highly available using clustering software). Refer to the redbook A Practical Guide to DB2 UDB Data Replication V8, SG24-6828, for details about DB2 replication.