Bus members
The members of a service integration bus can be application servers, server clusters, or IBM MQ servers. Bus members that are application servers or server clusters contain messaging engines, which are the application server components that provide asynchronous messaging services. Bus members that are IBM MQ servers provide a direct client connection between a service integration bus and queues on an IBM MQ queue manager.
To use a service integration bus, add at least one application server or server cluster as a bus member. We can also add bus members that are IBM MQ servers; service integration uses these bus members to write messages to, and read messages from, IBM MQ queues.
When we add an application server or a server cluster as a bus member, a messaging engine for that bus member is created automatically. If the bus member is an application server, it can have only one messaging engine. To host queue-type destinations, the messaging engine includes a message store where, if necessary, it can hold messages until consuming applications are ready to receive them, or preserve messages in case the messaging engine fails. If the bus member is a server cluster, it can have additional messaging engines to provide high availability or workload sharing characteristics. If the bus member is a IBM MQ server, it does not have a messaging engine, but it lets we access IBM MQ queues directly from IBM MQ queue managers and (for IBM MQ for z/OS ) queue-sharing groups.
A WAS application does not have to be running on a service integration bus member to use its messaging services. If necessary, WAS automatically provides a connection to a suitable bus member.
Figure 1. Bus members
If required, we can remove members from a bus. However, this action deletes any messaging engines associated with a bus member, including knowledge of any messages held by the message store for those messaging engines. Therefore, we must plan this action carefully.
When a bus member is deleted, the data source associated with this bus member is not automatically deleted, in case we are also using the data source for some other purpose. This also applies to bus members created using the default data source: the data source is not automatically deleted and we must remove it manually. You need not remove the default data sources because they use a universal unique identifier (UUID) in the name of the Apache Derby database. However, we might choose to delete the data source to avoid wasting disk space.