Businesses are increasingly becoming aware of the advantages ofestablishing an intranet or of connecting processors to a LAN. Forexample, you might connect some AIX processors in the form of an SP2.Processors that are linked in these ways benefit from support fromeach other and have access to a far wider range of programs and data.In the same way, WebSphere MQ queue managers can be connected toform a cluster. This facility is available to queue managers on alloperating systems.You can connect the queue managers by using any of thecommunications protocols that are available on your operating system.That is, TCP or LU6.2 on any operating system, NetBIOS, or SPX onWindows.Connections on more than one protocol can exist within a cluster. If youtry to make a connection to a queue manager by using a protocol that itdoes not support, the channel does not become active.
One of the first decisions that must be made when setting up a cluster, is todetermine the queue managers that are to have a full repository. All other queuemanagers must have a predefined CLUSSDR channel to one of the full repositoryqueue managers in the cluster.You might call QM1 the primary repository, and QM4 the secondary, but thisrelationship is true only from the point of view of QM2. Both full repository QMGRshave equal rights and functions, as to the cluster.The full and partial repositories store queue manager information like the creationof a new queue for 30 days.To prevent this data from expiring, the queue manager resends information aboutthemselves after 27 days. When data expires, it is not immediately removed; insteadit has a grace period of 60 days. If during the grace period, no changes occur thenthe data is removed. This grace period provides a queue manager that wastemporarily out of service at the expiry date the right to rejoin if it does not staydisconnected from the cluster for 90 days. Then, that queue manager no longer ispart of the cluster.
You do not need to alter any of your applications if you are goingto set up a simple WebSphere MQ cluster. The applications namethe target queue on the MQOPEN call as typical and are notconcerned about the location of the queue manager.However, if you set up a cluster in which there are multipledefinitions for the same queue , you must review your applicationsand modify them as necessary.Additional information — Bind on group is a new feature added inWebSphere MQ V7.1.Addition of this feature includes two new message flags within themessage descriptor of messages:• Last message in group: MQMF_LAST_MSG_IN_GROUP• All other messages in group: MQMF_MSG_IN_GROUP