A cloned broker is a broker for which you have defined one or more clones; the subscription table of a cloned broker is replicated to all other brokers with which it is cloned.
When a subscriber requests a subscription from a cloned broker, the subscription is also sent to each of the clones of that broker.
Use cloned brokers to improve the availability of your publish/subscribe system. By defining cloned brokers on different computers, you make sure that a publication is delivered to a subscriber even when one of the computers is unavailable.
If two brokers are clones within a collective, duplicate messages might be sent to subscribers that are registered with brokers inside that collective.
Use the mqsichangeproperties command to define cloned brokers; the property clonedPubSubBrokerList is used to do this.