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| boydl |
 Posted: Fri May 27, 2005 2:34 am Post subject: How MQ achieve persistent messaging? |
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Novice
Joined: 05 Feb 2003
Posts: 16
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Hi all,
I hv got a fundamental question to ask...
For persistent messaging, does MQ write to disk first and then sends the message across or does it do a send first b4 persisting to disk? Wont there be an IO overhead if it is the first case? Also, if it is the 1st case, how would it remove the message once the message is delivered?
What is the difference with JMS persistent and non-persistent messaging?
regards
blim |
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| sebastianhirt |
| Posted: Fri May 27, 2005 2:53 am Post subject: |
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Yatiri
Joined: 07 Jun 2004
Posts: 620
Location: Germany
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Hi,
Check out this presentation. It has a nice little paragraph about how persistent messaging does work
http://irm.state.nc.us/NCSB/KnowledgeBase/MQTechConf/000-linked%20files/m37.pdf
| Quote: |
| For persistent messaging, does MQ write to disk first and then sends the message across or does it do a send first b4 persisting to disk? |
Every Persistent message is written twice to the disk. 1st to the log then to the queue file
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| Wont there be an IO overhead if it is the first case? |
Yes there is an IO Overhead. Check out the performance relate Fix Packs. There should be an evaluation on how big it is
Hope this helps
cheers
Sebastian |
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| emiranda |
| Posted: Fri May 27, 2005 7:29 am Post subject: Re: How MQ achieve persistent messaging? |
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Disciple
Joined: 21 Nov 2002
Posts: 196
Location: Dublin, Ireland
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| boydl wrote: |
| Also, if it is the 1st case, how would it remove the message once the message is delivered? |
I guess the qmgr knows the message was sucessful delivered (mca's negotiation) and deletes the message 
_________________
Warm Regards,
EM |
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| EddieA |
| Posted: Fri May 27, 2005 8:58 am Post subject: |
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Jedi
Joined: 28 Jun 2001
Posts: 2453
Location: Los Angeles
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| Quote: |
| What is the difference with JMS persistent and non-persistent messaging? |
The same as the difference with MQ persistent and non-persistent messages.
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| I guess the qmgr knows the message was sucessful delivered (mca's negotiation) and deletes the message |
Close. The MCA does a GET inside a UOW to transmit the message. When it gets conformation that the message has been received it commits the GET. This does the same kind of actions as described for the put. That causes the update of the log to say the message has been read, and then it removes it from the queue, as opposed to adding it. Again, more I/O overhead.
Cheers,
_________________
Eddie Atherton
IBM Certified Solution Developer - WebSphere Message Broker V6.1
IBM Certified Solution Developer - WebSphere Message Broker V7.0 |
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| boydl |
| Posted: Sun May 29, 2005 8:41 pm Post subject: |
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Novice
Joined: 05 Feb 2003
Posts: 16
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Thanks Sebastian for the URL ...it was very informative.
Thanks Emiranda and EddieA for yr response on the MQ removes messages from queue once it has been delivered.
Is there anywhere that i can go to.. to get more "under the hood" information on MQSeries?
regards
BL |
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| emiranda |
| Posted: Mon May 30, 2005 12:30 am Post subject: |
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Disciple
Joined: 21 Nov 2002
Posts: 196
Location: Dublin, Ireland
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Eventualy you can find some good discussion on the net. Personaly I don't have any other source than the IBM's manuals... the problem is we almost never have the time to go to the manuals and read them cool-headed, without a problem rushing you...
And, of course, play with it... as much as you can!
Cheerio 
_________________
Warm Regards,
EM |
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| sebastianhirt |
| Posted: Mon May 30, 2005 1:10 am Post subject: |
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Yatiri
Joined: 07 Jun 2004
Posts: 620
Location: Germany
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Yeah, the manuals are really good. If you can pursuade your manager, let him send you to the various MQ classes at IBM.
I can recomend you the Clustering one (If you use clustering).
The MQ Admin II I found pretty good too. There you'll get a lot of "under the hood" information about channels, MCAs...
Some people here where saying the debugging techniques one is really good, too. But as I didn't visited it, I can't really give a statement. |
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