Sun Java System Application Server Enterprise Edition 8.1 2005Q2 Developer's Guide

Distributed Sessions and Persistence

A distributed session can run in multiple Application Server instances, provided the following criteria are met:

Note –

Contrary to the Servlet 2.4 specification, Application Server does not throw an IllegalArgumentException if an object type not supported for failover is bound into a distributed session.

Keep the distributed session size as small as possible. Session size has a direct impact on overall system throughput.

A servlet that is not deployed as part of a web application is implicitly deployed to a default web application and has the default ServletContext. The default ServletContext is not distributed. (A web application with an empty context root does not have the default ServletContext.)

In the event of an instance or hardware failure, another server instance can take over a distributed session, with the following limitations:

For information about how to work around these limitations, see the Sun Java System Application Server Enterprise Edition 8.1 2005Q2 Deployment Planning Guide.

In the following table, No indicates that failover for the object type might not work in all cases and that no failover support is provided. However, failover might work in some cases for that object type. For example, failover might work because the class implementing that type is serializable.

For more information about the InitialContext, see Accessing the Naming Context. For more information about transaction recovery, see Chapter 12, Using the Transaction Service. For more information about Administered Objects, see Creating Physical Destinations.

Table 5–4 Object Types Supported for J2EE Web Application Session State Failover

Java Object Type  

Failover Support  

Stateless session, stateful session, and entity bean local home reference, local object reference 


Colocated and distributed stateless session, stateful session, and entity bean remote home reference, remote reference 


JNDI Context 

Yes, InitialContext and java:comp/env


Yes, but if the instance that fails is never restarted, any prepared global transactions are lost and might not be correctly rolled back or committed 

JDBC DataSource 


JavaTM Message Service (JMS) ConnectionFactory, Destination


JavaMailTM Session


Connection Factory 


Administered Object 


Web service reference 


Serializable Java types