Brokers can also be linked to form units known as clusters. Brokers that form a cluster function as a single logical Broker. All Brokers in a cluster maintain the same set of document types and client groups. However, each Broker supports its own set of clients. In a cluster, published documents are not forwarded to other Brokers (peers).

Clusters support client-side load balancing and failover by allowing you to use JMS clustering policies to distribute message traffic between multiple Brokers, while still treating the Brokers as a single operational unit.

When Brokers operate in a cluster, they maintain the same set of document types and client group definitions. (These objects are initially synchronized when a Broker joins a cluster.) Any changes that occur to these objects on one Broker, are automatically propagated to the other Brokers in the cluster.

The Brokers that are members of a cluster can reside on any Broker Server. The following figure shows a cluster made up of three Brokers on two Broker Servers.

For information about working with clusters, see Managing Clusters.