Assured delivery and MQ setup

Paul Clarke

2013-12-05 10:37:45 UTC

The concept of 'assured delivery' doesn't really apply to applications,
whether locally connected or via a client. When you are using the MQI the
Application gets told what the result of the call was via the reason code. A
zero reason code clearly means all is well (so far) but doesn't imply that
the message will definitely make it to the target destination (or indeed
that it will make it to the first queue).

Essentially the rules for an application are the same whether locally
connected or over a client. Even locally connected you can have situation
where the state of the last call is 'in doubt'. Consider an application
issuing an MQCMIT() call. What happens if something issues 'endmqm -i' at
just the right moment and the application gets back MQRC_CONNECTION_BROKEN.
Did the transaction commit or not ? And of course there are dozens of other
things that can go wrong including a power cut which would effectively give
the same issue. In many cases the application doesn't need to know, but if
it does then it should write suitable code so it can find out.

The bottom line is that the programming model is the same for clients as for
local applications it's just that over a client more things can go wrong and
the windows of opportunity for system failure tend to be larger.

Cheers,
Paul.

Paul Clarke
www.mqgem.com
-----Original Message-----
From: Costa, D. (Damian)
Sent: Thursday, December 05, 2013 10:24 AM
To: MQSERIES-0lvw86wZMd9k/bWDasg6f+***@public.gmane.org
Subject: Assured delivery and MQ setup

Hi all,
Does an MQ client still give one assured delivery or only a local bindings
mode ? my guess is no as the state of the last call might be in doubt if
there is a qmgr failure of some type.
Thanks.

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