WebSphere Application Server V7.0: Concepts ... - IBM Redbooks

To ensure that the messaging engine runs on one particular server in the cluster,
(for example, if you have one primary server and one backup server, or if you
want the messaging engine to only run on a small group of servers within the
cluster), you must specifically configure it by defining the preferred server for the
messaging engine. Each messaging engine on a service integration bus belongs
to one high availability group. A policy assigned to the group at runtime controls
the members of each group. This policy determines the availability
characteristics of the messaging engine in the group and is where preferred
servers are designated. Be careful not to reduce or remove the high availability of
the messaging engine by having a list of preferred servers that is too restricted.
To obtain workload management across a bus with a cluster, you need to create
additional messaging engines and assign the messaging engines to a preferred
server. The messaging engines run simultaneously with queues partitioned
across them. You might need to consider clustering some application server if
you have not already.
10.5.4 Planning for reliability
The JMS specification supports two modes of delivery for JMS messages:
► Persistent
► Non-persistent
The WebSphere administrator can select the mode of delivery on the JMS
destination (queue/topic) configuration:
► Application (persistence is determined by the JMS client)
► Persistent
► Non-persistent
Messages can also have a quality of service attribute that specifies the reliability
of message delivery. Different settings apply depending on the delivery mode of
the message. The reliability setting can be specified on the JMS connection
factory and, for the default messaging provider, on the bus destination. Reliability
settings set at the connection factory apply to all messages using that connection
factory, though you can opt to let the reliability settings be set individually at the
bus destination. Each reliability setting has different performance characteristics.
The settings are as follows:
► Best effort non-persistent
► Express non-persistent
► Reliable non-persistent
► Reliable persistent
► Assured persistent
Chapter 10. Messaging 353