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| UOW Type - XA versus Qmgr What am I looking at? |
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| PeterPotkay |
 Posted: Tue Sep 23, 2014 9:32 am Post subject: UOW Type - XA versus Qmgr What am I looking at? |
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Poobah
Joined: 15 May 2001
Posts: 7722
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I have a JMS ap with 6 input handles on a queue. One of the six shows UOW Type = XA, and the other 5 are = to QMGR.
What does that mean?
We are struggling with getting backout processing to work. It seems the same 2 messages are being backed out to the input queue, picked up, moved to the backout queue, rolled back to the input queue, picked up, moved to the backout queue, repeat.
I think that means they just need to commit the transaction. But exactly when? How are they notified by the JMS MQ Libraries "Hey, I backed something out for you. You wanna commit now?"
And why do 5 of the 6 input threads have a different value for UOW Type?
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Peter Potkay
Keep Calm and MQ On
Last edited by PeterPotkay on Wed Sep 24, 2014 5:43 am; edited 1 time in total |
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| fjb_saper |
| Posted: Tue Sep 23, 2014 7:47 pm Post subject: |
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Grand High Poobah
Joined: 18 Nov 2003
Posts: 20756
Location: LI,NY
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Well you'd better check your bothresh on the queue. If it is not set the backout / reprocess can go on forever....
On the other hand Using JMS you can decide to do a single phase commit session or a multi-phase commit session. The Multi-phase commit session is also called XA session because the XA protocol is used for multi-phase commit.
The session sets your transaction boundaries.The app server's transaction setup can override any other transactional setup you may have. This is why when you use JMS it is always good to set up the transactionality in the MDB's explicitly using the deployment descriptor.
Have fun 
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| PeterPotkay |
| Posted: Wed Sep 24, 2014 5:37 am Post subject: |
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Poobah
Joined: 15 May 2001
Posts: 7722
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The input queue does have the BO Thresh Hold set to 1, and a valid BO Queue name.
The backout is happening. I can see it by looking at the stats in QPASA for the input queue and the base queue, and occasionally I catch a peek of the messages and their every increasing backout count by wailing away at the refresh button in my MO71 view of that queue.
Watching this some more I see some of the input threads occasionally show UOW Type = "XA" while the others show "Qmgr". Are these the threads grabbing a message and being put into a global UOW by the Transaction manager, and only then does their UOW Type change to XA?
I'm not clear on how the Transaction Manager knows to commit when a message is backed out to the backout queue if that happens 'under the covers' and automatically by the MQ JMS library. Do they send some sort of acknoledgement to the transaction manager saying a backout occured, go ahead and commit?
I seem to have a foggy recollection that its not until the next successful message is processed and commited does the backout of the previous unrelated message get commited. True?
Right now the same 2 poisened messages are spinning between the input queue and the backout queue. No commit is happening. Maybe all that needs to happen is a drop of a good message?
This is playing around in DEV with a new app.
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Peter Potkay
Keep Calm and MQ On
Last edited by PeterPotkay on Wed Sep 24, 2014 5:45 am; edited 1 time in total |
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| mqjeff |
| Posted: Wed Sep 24, 2014 5:42 am Post subject: |
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Grand Master
Joined: 25 Jun 2008
Posts: 17447
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You also, unfortunately, need to look at what the app is doing and how it's configured in the app server.
Container managed persistence?
With WAS, at least, and maybe with anything else using the MQ RA, it's the App server that actually acts as the XA Resource Manager, *not* the queue manager. The queue manager participates as an XA resource, but doesn't do the coordination.
That probably explains the connection with the XA on it. |
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| PeterPotkay |
| Posted: Wed Sep 24, 2014 7:51 am Post subject: |
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Poobah
Joined: 15 May 2001
Posts: 7722
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| PeterPotkay wrote: |
I seem to have a foggy recollection that its not until the next successful message is processed and commited does the backout of the previous unrelated message get commited. True?
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True!
http://www.mqseries.net/phpBB2/viewtopic.php?t=49417
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Peter Potkay
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