Application Server delivers messages randomly to MDBs having same ClientID . The ClientID is required for durable subscribers.
For non-durable subscribers in which the ClientID is not configured, all instances of a specific MDB that subscribe to same topic are considered equal. When an MDB is deployed to multiple instances of the Application Server, only one of the MDBs receives the message. If multiple distinct MDBs subscribe to same topic, one instance of each MDB receives a copy of the message.
To support multiple consumers using the same queue, set the maxNumActiveConsumers property of the physical destination to a large value. If this property is set, MQ allows up to that number of MDBs to consume messages from same queue. The message is delivered randomly to the MDBs. If maxNumActiveConsumers is set to -1, there is no limit to the number of consumers.