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MQMB&WAS
PostPosted: Mon Aug 30, 2021 1:32 am    Post subject: DLQ at source qmgr Reply with quote

Centurion

Joined: 12 Jun 2016
Posts: 130

Hello experts,

I have APP1 putting messages to QMGR1 and the messages are supposed to go to QMGR2 for APP2 to consume. Both the qmgrs have DLQ defined.

In what scenarios can the messages put by APP1 go to the DLQ on QMGR1?

Thanks
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bruce2359
PostPosted: Mon Aug 30, 2021 4:09 am    Post subject: Reply with quote

Poobah

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

When MQ internals put a message in the DLQ, a dead letter header is also put to the DLQ. Examine the DLH (dead letter header) in the dead letter queue to identify the ReasonCode.
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MQMB&WAS
PostPosted: Mon Aug 30, 2021 7:01 am    Post subject: Reply with quote

Centurion

Joined: 12 Jun 2016
Posts: 130

bruce2359 wrote:
When MQ internals put a message in the DLQ, a dead letter header is also put to the DLQ. Examine the DLH (dead letter header) in the dead letter queue to identify the ReasonCode.



I don't have a message in the DLQ right now. I'm just trying to understand all the possible scenarios of when a message can go to the DLQ on the source qmgr.
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bruce2359
PostPosted: Mon Aug 30, 2021 8:47 am    Post subject: Reply with quote

Poobah

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

If the Sender channel specifies CONVERT(YES) and the message data cannot be converted, the message will be moved to the DLQ on the Sender side.
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Lex Orandi, Lex Credendi, Lex Vivendi. As we Worship, So we Believe, So we Live.
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MQMB&WAS
PostPosted: Mon Aug 30, 2021 5:03 pm    Post subject: Reply with quote

Centurion

Joined: 12 Jun 2016
Posts: 130

bruce2359 wrote:
If the Sender channel specifies CONVERT(YES) and the message data cannot be converted, the message will be moved to the DLQ on the Sender side.


Thanks Bruce. Is this the only scenario?
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hughson
PostPosted: Mon Aug 30, 2021 10:52 pm    Post subject: Re: DLQ at source qmgr Reply with quote

Padawan

Joined: 09 May 2013
Posts: 1914
Location: Bay of Plenty, New Zealand

MQMB&WAS wrote:
In what scenarios can the messages put by APP1 go to the DLQ on QMGR1?

Here are the ones I can think of:
  • MAXMSGL on CHANNEL is less than message size (and therefore also less than MAXMSGL of XmitQ). Always ensure CHANNEL and XmitQ have same MAXMSGL and you won't encounter this.
  • Data Conversion failures (which can only occur with CONVERT(YES) on the channel).
  • If the message doesn't have an MQXQH on the front - i.e. an application put a message DIRECTLY onto the XmitQ
  • If a message exit decided it didn't like the message
It is definitely a smaller list than that for the DLQ of QMGR2!

Cheers,
Morag
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MQMB&WAS
PostPosted: Tue Aug 31, 2021 7:01 pm    Post subject: Reply with quote

Centurion

Joined: 12 Jun 2016
Posts: 130

Thanks Morag and bruce.
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hughson
PostPosted: Thu Sep 02, 2021 1:44 am    Post subject: Reply with quote

Padawan

Joined: 09 May 2013
Posts: 1914
Location: Bay of Plenty, New Zealand

A wrote a blog post prompted by this question: Dead-letter Queue use by IBM MQ Channels

Cheers,
Morag
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exad3545
PostPosted: Sat Oct 28, 2023 11:15 pm    Post subject: Reply with quote

Newbie

Joined: 28 Oct 2023
Posts: 3

Here's a list of potential reasons I can come up with:

When the MAXMSGL on the CHANNEL is set lower than the message size, which is also less than the MAXMSGL of the XmitQ. To avoid this, make sure that the MAXMSGL values for both the CHANNEL and XmitQ match, preventing this issue.

Data conversion failures, which are applicable only when CONVERT(YES) is enabled on the channel.

If a message lacks an MQXQH at the beginning, which indicates that an application directly placed the message onto the XmitQ.

When a message exit determines that the message doesn't meet its criteria.

It's worth noting that this list is notably shorter than the one for the DLQ of QMGR2, offering a streamlined perspective on potential issues.
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gbaddeley
PostPosted: Sun Oct 29, 2023 2:27 pm    Post subject: Reply with quote

Jedi

Joined: 25 Mar 2003
Posts: 2492
Location: Melbourne, Australia

exad3545 wrote:
Here's a list of potential reasons I can come up with:
When the MAXMSGL on the CHANNEL is set lower than the message size, which is also less than the MAXMSGL of the XmitQ. To avoid this, make sure that the MAXMSGL values for both the CHANNEL and XmitQ match, preventing this issue.

This will not avoid the issue, as the app could still put a message that is larger than MAXMSGL.
Quote:
Data conversion failures, which are applicable only when CONVERT(YES) is enabled on the channel.
If a message lacks an MQXQH at the beginning, which indicates that an application directly placed the message onto the XmitQ.

An app can still place a message onto the XmitQ if it includes a MQXQH.
Quote:

When a message exit determines that the message doesn't meet its criteria.
It's worth noting that this list is notably shorter than the one for the DLQ of QMGR2, offering a streamlined perspective on potential issues.

It appears that you are merely paraphrasing previous responses, and not adding anything to the conversation. You could be mistaken for being an AI chat bot that can process meaning in sentences but not have deep understanding of the content.
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