Checkpointing saves a stateful session bean (SFSB) state to the HADB so that if the server instance fails, the SFSB is failed over to another instance in the cluster and the bean state recovered. The size of the data being checkpointed and the frequency at which checkpointing happens determine the additional overhead in response time for a given client interaction.
You can enable SFSB checkpointing at numerous different levels:
For the entire server instance or EJB container
For the entire application
For a specific EJB module
Per method in an individual EJB module
For best performance, specify checkpointing only for methods that alter the bean state significantly, by adding the <checkpointed-methods> tag in the sun-ejb-jar.xml file.