Sun Microsystems 820434310 manual Stateless Session Beans, Read-Only Entity Beans

EJB Performance Tuning

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.

Stateless Session Beans

Stateless session beans are more readily pooled than entity or the stateful session beans. Valid values for steady-pool-size, pool-resize-quantity and max-pool-size are the best tunables for these type of beans. Set the steady-pool-size to greater than zero if you want to pre-populate the pool. This way, when the container comes up, it creates a pool with steady-pool-size number of beans. By pre-populating the pool it is possible to avoid the object creation time during method invocations.

Setting the steady-pool size to a very large value can cause unwanted memory growth and can result in large garbage collection times. pool-resize-quantity determines the rate of growth as well as the rate of decay of the pool. Setting it to a small value is better as the decay behaves like an exponential decay. Setting a small max-pool-size can cause excessive object destruction (and as a result excessive object creation) as instances are destroyed from the pool if the current pool size exceeds max-pool-size.

Read-Only Entity Beans

Read-only entity beans cache data from the database. Application Server supports read-only beans that use both bean-managed persistence (BMP) and container-managed persistence (CMP). Of the two types, CMP read-only beans provide significantly better performance. In the EJB lifecycle, the EJB container calls the ejbLoad() method of a read-only bean once. The container makes multiple copies of the EJB component from that data, and since the beans do not update the database, the container never calls the ejbStore() method. This greatly reduces database traffic for these beans.

If there is a bean that never updates the database, use a read-only bean in its place to improve performance. A read-only bean is appropriate if either:

Chapter 2 • Tuning Your Application 43