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| kash3338 |
 Posted: Fri Apr 27, 2012 9:08 pm Post subject: Backout Queue functionality |
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Shaman
Joined: 08 Feb 2009
Posts: 709
Location: Chennai, India
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Hi,
I have a doubt regarding the Backout queue of a queue in MQ. Is it the MQ that moves the messages to Backout queue when the Backout count exceeds or is it the client application that does move the message to Backout queue?
ASFAIK its the client that moves the message to the Backout queue and not the MQ. In that case, why do we define Backout queue in MQ and why is it a property at MQ level? |
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| fjb_saper |
| Posted: Fri Apr 27, 2012 11:04 pm Post subject: |
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Grand High Poobah
Joined: 18 Nov 2003
Posts: 20756
Location: LI,NY
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Because some clients like JMS do it for you! 
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MQ & Broker admin |
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| kash3338 |
| Posted: Fri Apr 27, 2012 11:47 pm Post subject: |
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Shaman
Joined: 08 Feb 2009
Posts: 709
Location: Chennai, India
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| fjb_saper wrote: |
| Because some clients like JMS do it for you! |
MQ itself is a JMS provider. My question is, why do we need to define the Backout queue in MQ settings when its not the MQ which takes care of moving a message there. If the client application needs to move the message, it can move of any of the queue right? |
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| exerk |
| Posted: Sat Apr 28, 2012 1:10 am Post subject: |
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Jedi Council
Joined: 02 Nov 2006
Posts: 6339
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| kash3338 wrote: |
| My question is, why do we need to define the Backout queue in MQ settings when its not the MQ which takes care of moving a message there. If the client application needs to move the message, it can move of any of the queue right? |
And my answers are:
1. It's a convenient place to hold the information;
2. If the back=out queue needs to change, there is no need to change code in the client application, or modify any client initialisation files.
And I know that certain things should not be hard-coded, but we've all seen it done!
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| kash3338 |
| Posted: Sat Apr 28, 2012 5:27 am Post subject: |
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Shaman
Joined: 08 Feb 2009
Posts: 709
Location: Chennai, India
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| exerk wrote: |
2. If the back=out queue needs to change, there is no need to change code in the client application, or modify any client initialisation files.
And I know that certain things should not be hard-coded, but we've all seen it done! |
Yes the point that certain things should not be hard-coded is correct, but it still does not answer my question... Why is this coupled with MQ? These things should be taken care by the client application either by using some config files or database. |
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| mqjeff |
| Posted: Sat Apr 28, 2012 5:33 am Post subject: |
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Grand Master
Joined: 25 Jun 2008
Posts: 17447
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| kash3338 wrote: |
| Why is this coupled with MQ? |
| exerk wrote: |
| It's a convenient place to hold the information; |
It's there as a convenience.
It also allows for things to be set administratively. Without having to teach your administrators where your config file is and how to properly set it.
So, again.
It's a convenience for both the developer and the administrator. |
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| mvic |
| Posted: Sat Apr 28, 2012 6:14 am Post subject: Re: Backout Queue functionality |
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Jedi
Joined: 09 Mar 2004
Posts: 2080
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| kash3338 wrote: |
| why is it a property at MQ level? |
MQ has been implemented this way for many years.. some people will now be relying on it, so it's not going to change.
Applications can choose to use it, or not. MQ's JMS will go further than plain MQ in using it, if you choose. |
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| bruce2359 |
| Posted: Sat Apr 28, 2012 10:13 am Post subject: Re: Backout Queue functionality |
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Poobah
Joined: 05 Jan 2008
Posts: 9469
Location: US: west coast, almost. Otherwise, enroute.
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| kash3338 wrote: |
| ... why do we define Backout queue in MQ and why is it a property at MQ level? |
WMQ is object-oriented. Objects (including the qmgr) have attributes, and attributes have values.
Some attributes are pervasive across a specific qmgr, like the DEADQ attribute. Some attributes only apply to a specific object (queue, in this instance). Attribute values are changed by system admins, and in some cases by applications.
The purpose and use of a backout queue is thoroughly documented in the WMQ Application Programming Reference and WMQ Application Programming Guide. It is used by and for applications.
So, your phrasing of why is it a property at MQ level is somewhat inaccurate in the sense that all objects (and their 'properties') are owned by the qmgr; and therefore, there is no other place for these types of properties.
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