2.6.5 Stateful session bean failover
One significant high availability improvement introduced in WAS V6 is the failover support for stateful session beans, which means that the state information maintained by a stateful session bean can survive various types of failures now. This is achieved by using the functions of the Data Replication Service (DRS) and server workload management (WLM).
Unlike the failover support for stateless session beans, the highly available stateful session bean does not utilize a redundant array of stateful session bean instances but rather replicates its state in a highly available manner such that when an instance fails, the state can be recovered and a new instance can take the failed instance's place. The state replication of a stateful session bean to another instance is handled by DRS.
Stateful session bean failover is provided by WebSphere as a runtime feature. Use the WAS console to enable or disable the failover support. Depending on the scope of the failover target, you can enable or disable the stateful session failover at the following three levels:
- EJB container
- Enterprise application
- EJB module
This feature provides great flexibility to users who want to enable failover under the following circumstances:
- For all applications except for a single application, enable failover at the EJB container level and override the setting at the application level to disable failover for the single application.
- For a single installed application, disable failover at the EJB container level and then override the setting at the application level to enable failover for the single application.
- For all applications except for a single module of an application, enable failover at the EJB container level, then override the setting at the module application level to disable failover for the single module.
- For a single installed EJB module, disable failover at the EJB container level and then override the setting at the EJB module level to enable failover for the single EJB module.