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MQSeries.net Forum Index » Multiphase Commit » XA transaction for remote queue

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karthick_3d
PostPosted: Fri Jun 10, 2016 6:41 am    Post subject: XA transaction for remote queue Reply with quote

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Joined: 10 Jun 2016
Posts: 4

All,
I am new to this group. I was searching for some discussions around using XA transaction using Remote Queues. But I didnt manage to find exactly what I am after.
If I am creating a Remote Queue to drop a message to a different Queue manager using a sender/receiver channel, Would XA transaction work without any issues. i.e. if the transaction rollback at the end, would MQ ensures the message doesnt reach the remote Queue?

thanks
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bruce2359
PostPosted: Fri Jun 10, 2016 6:58 am    Post subject: Reply with quote

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Joined: 05 Jan 2008
Posts: 9394
Location: US: west coast, almost. Otherwise, enroute.

A QRemote definition is not a queue. When the QR def is MQOPENed, subsequent MQPUTs are to a transmission queue (a QLocal with xmitq attribute). These MQPUTs may be in a UofW that the app MQCMITs or MQBACKs. Your UofW ends here.

The Sender Message Channel Agent moves the message from the transmission queue down the network to the Receiver MCA, which MQPUTs the message in the destination queue (or dead-letter-queue).
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Vitor
PostPosted: Fri Jun 10, 2016 7:12 am    Post subject: Reply with quote

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Joined: 11 Nov 2005
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Location: Texas, USA

You need to think about what is included in the transaction's unit of work, and what's participating in terms of software. If you have (for example) the application, the queue manager and the database all synchronized through XA and you've put the message in the same unit of work as the database changes, then neither the put nor the database changes are committed until the transaction is committed. If the transaction is rolled back, all are rolled back.

Likewise, if the message can't be put (the xmitq is full) then the database changes would be rolled back. If the message wasn't put under syncpoint, then it wouldn't matter what happened to the transaction.

And none of this has any effect on the queue that is remote (i.e. where the remote queue is pointing).
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karthick_3d
PostPosted: Fri Jun 10, 2016 8:51 am    Post subject: Reply with quote

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Joined: 10 Jun 2016
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Thanks, I see it should work similar to a local queue participating in XA transaction. We have applications which would update multiple databases and MQ . So If there is a rollback due to any reason, local queue updates (GET/PUT) would rollback. I should expect the same behavior for remote queues as well. I will write some test application to test the same.
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Vitor
PostPosted: Fri Jun 10, 2016 9:06 am    Post subject: Reply with quote

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Location: Texas, USA

karthick_3d wrote:
I should expect the same behavior for remote queues as well.


As my worthy associate points out, a qremote isn't a queue but an indirection point to a specific type of local queue. So of course it works the same as for the other type of local queue. A remote queue is a local queue hosted by a queue manager you're not connected to, and is unaffected by anything you do locally.
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gbaddeley
PostPosted: Tue Jun 14, 2016 10:59 pm    Post subject: Reply with quote

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Joined: 25 Mar 2003
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karthick_3d wrote:
Thanks, I see it should work similar to a local queue participating in XA transaction. We have applications which would update multiple databases and MQ . So If there is a rollback due to any reason, local queue updates (GET/PUT) would rollback. I should expect the same behavior for remote queues as well. I will write some test application to test the same.

For putting messages to QREMOTE objects, the commit / rollback occurs on the transmission queue.

MQ conducts a separate UOW for the Message Channel Agent to deliver the message to the destination QLOCAL on the remote queue manager. So even after your app commits, the message still has to go through the MCA UOW before it is visible on the destination QLOCAL. If there are issues with starting or running channels, there may be a delay.
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bruce2359
PostPosted: Wed Jun 15, 2016 5:29 am    Post subject: Reply with quote

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Joined: 05 Jan 2008
Posts: 9394
Location: US: west coast, almost. Otherwise, enroute.

gbaddeley wrote:
karthick_3d wrote:
Thanks, I see it should work similar to a local queue participating in XA transaction. We have applications which would update multiple databases and MQ . So If there is a rollback due to any reason, local queue updates (GET/PUT) would rollback. I should expect the same behavior for remote queues as well. I will write some test application to test the same.

For putting messages to QREMOTE objects, the commit / rollback occurs on the transmission queue.

MQ conducts a separate UOW for the Message Channel Agent to deliver the message to the destination QLOCAL on the remote queue manager. So even after your app commits, the message still has to go through the MCA UOW before it is visible on the destination QLOCAL. If there are issues with starting or running channels, there may be a delay.

And, presuming that the consuming app MQGETs the message in SYNCPOINT (in a UofW), three separate and distinct UofW's take place:
UofW 1. The producing app MQPUTs the original message to the xmitq in SYNCPOINT.
UofW 2. The sending side MCA MQGETs the message from the xmitq, and transmits it down the network to the receiving side MCA, which MQPUTs the message into the destination queue (or Dead-Letter-Queue - all within the same SYNCPOINT.
UofW 3. The consuming app MQGETs the message from the destination queue in SYNCPOINT.
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