You can create clusters of supported application servers.
Application Engine/Workplace XT is an enterprise application running on a Java™ application server and should be made highly available by using either of the following configurations:
An administrative server manages a number of application server instances. Applications and configuration changes are implemented by using an administrative server/interface and sent to each cluster node.
In this type of configuration the application server software provides the components to build and deploy the highly available enterprise application.
JBoss application server clusters do not use a separate administrative server, and configuration changes are implemented on each cluster node separately.
A number of separate server instances run independently behind a load-balancer or proxy device. No central administration server is used. You must install and deploy on each farm node.