Queue managers that are connected together into a distributed publish/subscribe topology share a common federated topic space. Subscriptions created on one queue manager can receive messages published by an application connected to another queue manager in the topology.
We can control the extent of topic spaces created by connecting queue managers together in clusters or hierarchies. In a publish/subscribe cluster, a topic object must be 'clustered' for each branch of the topic space that is to span the cluster. In a hierarchy, each queue manager must be configured to identify its 'parent' in the hierarchy.
We can further control the flow of publications and subscriptions within the topology by choosing whether each publication and subscription is either local or global. Local publications and subscriptions are not propagated beyond the queue manager to which the publisher or subscriber is connected.