Joined: 04 Nov 2001 Posts: 10 Location: Waterloo Ontario
Can someone point me to some information as to why one would NOT want an MQ Clustered environement (in a multi queue manager multi server environment).
Or if someone want to offer their own opionion that would be great!
- currently only way to scale throughput of messages with multiple
cluster qmgrs and brokers
- adminstrative ease of use since you no longer define individual
channels between qmgrs (effort grows like N*N, N being the number
of qmgrs)
cons:
- administration can be unforgiving. Make a mistake during administration
and it can be hard to recover. Never administrate a cluster using
MQExplorer, use scripts only and test them well.
- messages can get trapped on a qmgr if either the qmgrs or its broker fail
until the recovery process restarts the service on a standby machine
(typically takes 5 minutes).
If you have a low latency, persistent message scenario you can get into
trouble here, since messages can exceed the maximum allowed processing
time (if its less than 5 minutes).
Currently the only *true* solution to this problem is using non-persistent
messaging with a request-reply protocol using message expiry. This is harder
to implement than persistent fire-and-forget (but also much faster).
MQ 5.3 introduces persistent shared queues on the 390 platform which allows
you to use persistent fire-and-forget even for those scenarios. Shared queues
are *real* cluster queues in the sense that they don't belong to a particular
qmgr but are external objects which reside in the so-called coupling facility
(basically a big bunch of shared memory) of the IBM 390. If one qmgr fails,
other will still be able to process the messages on the shared queue.
(MQ 5.2 only offers non-persistent shared queues which are not resistant to
coupling facility break-downs, although the latter are very unlikely).
_________________ Mathias Puetz
IBM/Central WebSphere Services
WebSphere Business Integration Specialist
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