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| Synchronising 1 message across 2 transactions |
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| darrylcook |
 Posted: Tue Jan 09, 2007 7:39 am Post subject: Synchronising 1 message across 2 transactions |
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Newbie
Joined: 19 Dec 2006
Posts: 6
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We are currently implementing changes to update our Client Server system to use MQ-Series as the message manager between the Client and the Server.
In the old system we used LU6.2 to maintain session between the client/server, so if the server transaction abended, the client wold know about it.
In the new system, LU6.2 is no more, the client drops a message on a Q, a trigger process is initiated to start a transaction in CICS, that transaction reads the next available message from the Q, decodes the data in the message and starts another CICS transaction (i.e the legacy transaction). At the end of processing on the server a message is dropped onto the reply Q for the client.
Our problem is synchronising the consumption of the message in one transaction based on the positive knowledge that the the other started CICS transaction has completed OK.
Whats the standard way of handling this scenario? Is it by using MQ CICS Bridge or a Message Broker?
Does anyone have an example of maintaining synchronisingn without using a third party product so that the original message is not consumed until you positively know that a further transaction has finished OK?
We are thinking of coding our own by sharing a resource between the program that reads the message and the driver program in the started transaction, using CICS ENQUEUE/DEQUEUE etc.. but we don't think this will be the most efficient method.
Any expertise greatly appreciated |
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| fjb_saper |
| Posted: Tue Jan 09, 2007 7:36 pm Post subject: |
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Grand High Poobah
Joined: 18 Nov 2003
Posts: 20756
Location: LI,NY
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Looks like you are not talking about multi-phase commit here but about compensated transactions. Read up on the concept.
Enjoy 
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| zpat |
| Posted: Wed Jan 10, 2007 2:30 am Post subject: |
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Jedi Council
Joined: 19 May 2001
Posts: 5866
Location: UK
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MQ can be used synchronously in application terms by waiting in your code for the reply message (to your request) before commiting the resource. No different to LU 6.2 in that sense.
If no reply is received in a set time then you rollback and ignore any reply that arrives later. This assumes that you wait for your particular reply messages by correlid (so the queues can be shared over multiple instances of the same application). Use an expiry time on replies so that orphaned messages are removed.
If you want to maintain state and process messages in an asynchronous application sense then you need to record the transaction's progress in a database and the aggregation nodes in WMIMB can do this for you. |
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