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| QSG's & Clusters - Stupid Question # 1248923759 |
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| DryHeatDave |
 Posted: Sun Apr 09, 2006 10:25 am Post subject: QSG's & Clusters - Stupid Question # 1248923759 |
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Apprentice
Joined: 21 Mar 2006
Posts: 28
Location: Phoenix, AZ
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Q. Does anyone have a 1-page explanation of the difference between a Queue-Sharing Group and a Cluster - in terms of what they ARE (I have lots of material in differences in how they are used).
I've searched this site & IBM & everywhere I can think of & nada.
NOTE: I'm only concerned about QSG's & Clusters in z/OS.
THX. 
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SCJP2
IBM Cert. Solutions Designer for Websphere MQ 5.3
Not a certified mainframer - just been doing it a real long time. |
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| wschutz |
| Posted: Sun Apr 09, 2006 11:02 am Post subject: |
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Jedi Knight
Joined: 02 Jun 2005
Posts: 3316
Location: IBM (retired)
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QSGs are described here:
http://publib.boulder.ibm.com/infocenter/wmqv6/v6r0/topic/com.ibm.mq.csqsat.doc/csq82d2.htm
The net is, you wind up defining queues that "live" in the coupling facility, which allows all other queue managers in the QSG to "MQGET" messages out of the queue. The advantage is you don't wind up with "stuck" messages, because even if the qmgr that put the message into the queue fails, other qmgrs in the QSG can still get the message.
Clustering is really just a simpler way to administer and distribute messages amongst queue managers. Once sent to a given qmgr, the message can become "stuck" if the qmgr fails. Of course, clustering is available on all qmgrs, shared queues only on zOS.
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-wayne |
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| PeterPotkay |
| Posted: Sun Apr 09, 2006 11:14 am Post subject: |
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Poobah
Joined: 15 May 2001
Posts: 7722
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and to mix it up even more, Shared queues can be clustered queues as well.
QM1 and QM2 are in a QSG, lets say QSG1. They live in a datacenter on the east coast.
QM3 and QM4 are in a different QSG, lets say QSG2. They live in a datacenter on the west coast.
All four QMs are in a cluster, called CLUSTER1
There are 2 queues, each called Homer. The first Homer queue lives in QSG1. The second lives in QSG2. If either QM1 or QM2 crash, messages are still gettable from the first Homer queue. And if QM3 or QM4 go down, messages are still gettable from the second Homer queue. Perhaps there is an app on QM5 sending to Homer. The messages get load balanced between the two Homer queues (power of clustering), and your risk of marooned messages on either QM becomes very small (power of QSGs). Marooned messages are still possible if say the whole data center goes down and you lose both QMs in the QSG.
Together, clusters and QSGs can make quite a highly available MQ system.
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Peter Potkay
Keep Calm and MQ On |
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| oz1ccg |
| Posted: Sun Apr 09, 2006 1:28 pm Post subject: |
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Yatiri
Joined: 10 Feb 2002
Posts: 628
Location: Denmark
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Hmm...
First, if we have messages in queue Homer on in QSG1 and the datacenter goes down, the messages there are stuck until the center is brought back to live..
If just QM1 goes down, QM2 will backout unfinisted work done by QM1, continue to process the messages in Homer.
In this case you don't see stuck messages, just a lower thruput until QM1 is brought back to live.
-- Lock it or Lose it -- 
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Regards, Jørgen
Home of BlockIP2, the last free MQ Security exit ver. 3.00
Cert. on WMQ, WBIMB, SWIFT. |
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| jefflowrey |
| Posted: Sun Apr 09, 2006 3:35 pm Post subject: |
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Grand Poobah
Joined: 16 Oct 2002
Posts: 19981
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| oz1ccg wrote: |
| the datacenter goes down, |
Then everyone panics for ten minutes, and a Disaster is declared, and DR training comes into effect.
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I am *not* the model of the modern major general. |
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