webMethods Broker runs as a service in a cluster. Within a cluster, there can be only a single instance of a Broker Server running at any given time. The spare Broker Server is stopped.

When a client makes a request to a Broker, the Broker handles the request much the same as in an unclustered environment. Although, in a clustered environment the Broker writes the client information to a shared disk instead of a private data store. The diagram below illustrates the flow of documents through a typical clustered environment.

If a Broker fails, subsequent requests for the session are redirected to a spare Broker in the cluster that is currently active and running, as shown in the diagram below.