Sun Java System Application Server Enterprise Edition 8.1 2005Q2 Performance Tuning Guide

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### Stateful Session Beans

When a stateful bean represents a user, a reasonable `max-cache-size` of beans is the expected number of concurrent users on the application server process. If this value is too low (in relation to the steady load of users), beans would be frequently passivated and activated, causing a negative impact on the response times, due to CPU intensive serialization and deserialization as well as disk I/O.

Another important variable for tuning is `cache-idle-timeout-in-seconds` where at periodic intervals of `cache-idle-timeout-in-seconds`, all the beans in the cache that have not been accessed for more than `cache-idle-timeout-in-seconds` time, are passivated. Similar to an HTTP session time-out, the bean is removed after it has not been accessed for `removal-timeout-in-seconds`. Passivated beans are stored on disk in serialized form. A large number of passivated beans could not only mean many files on the disk system, but also slower response time as the session state has to be de-serialized before the invocation.

#### Checkpoint only when needed

In high availability mode, when using stateful session beans, consider checkpointing only those methods that alter the state of the bean significantly. This reduces the number of times the bean state has to be checkpointed into the persistent store.

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