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| Operational note when adjusting queues to topics |
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| tczielke |
 Posted: Wed Nov 13, 2019 9:57 am Post subject: Operational note when adjusting queues to topics |
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Guardian
Joined: 08 Jul 2010
Posts: 941
Location: Illinois, USA
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I ran across this MQ behavior and did not see it posted on the internet, so I thought I would post it here in case it helps anyone else out.
Some MQ admins are familiar with the technique of changing a traditional queuing solution to use pub/sub for various reasons. Here are a couple of documented MQ examples of doing this:
Publish your MQ Events -> https://www.ibm.com/developerworks/community/blogs/aimsupport/entry/publish_your_mq_event_messages?lang=en
PUT message queue with duplicate messages -> https://www.ibm.com/support/pages/mq-you-want-put-message-queue-and-you-want-generate-duplicate-messages-other-queues
I followed these examples and did something similar with MQ Accounting.
One subtlety that I ran across with these documented approaches is that the DEFINE TOPIC does not specify the USEDLQ attribute. On a standard queue manager, this means the USEDLQ for the topic defaults to USEDLQ(ASPARENT) which eventually inherits the value of USEDLQ(YES). This means that when your local queue gets filled up for some reason, MQ will start putting these local PUTs on the DLQ! In my case, you now have accounting data filling your DLQ (which could easily be MAXDEPTH(999999999) and potentially filling your MQ /var/mqm filesystem!). Thankfully, I caught and corrected it before that happened. 
Probably, what would be better with these documented solutions is to add USEDLQ(NO) to the DEFINE TOPIC statements.
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| hughson |
| Posted: Wed Nov 13, 2019 2:14 pm Post subject: Re: Operational note when adjusting queues to topics |
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Padawan
Joined: 09 May 2013
Posts: 1959
Location: Bay of Plenty, New Zealand
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The "Publish your MQ Events" blog post was written before USEDLQ existed. It is also on a platform that will be sunset at the end of 2019. I am working through the posts that I wrote that are being sunset and moving them to a blog hosting platform that I control. I will move this one, and in the process, I will add USEDLQ as an option.
I have made a note to post back here when I have moved it.
Cheers,
Morag
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Morag Hughson @MoragHughson
IBM MQ Technical Education Specialist
Get your IBM MQ training here!
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| tczielke |
| Posted: Thu Nov 14, 2019 4:54 am Post subject: |
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Guardian
Joined: 08 Jul 2010
Posts: 941
Location: Illinois, USA
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Thank you for the information and working to improve the documentation on your side!
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| hughson |
| Posted: Sun Dec 01, 2019 8:13 pm Post subject: |
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Padawan
Joined: 09 May 2013
Posts: 1959
Location: Bay of Plenty, New Zealand
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Please note, a saved version of the blog post mentioned (which will be sunset soon), can now be found at Publish your MQ Event Messages
I have updated the post to use USEDLQ(NO) in the definitions, and added a little mention below of why you might want that.
Cheers,
Morag
_________________
Morag Hughson @MoragHughson
IBM MQ Technical Education Specialist
Get your IBM MQ training here!
MQGem Software |
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