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| anveshita |
 Posted: Mon Oct 05, 2009 2:37 pm Post subject: User-defined header |
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Master
Joined: 27 Sep 2004
Posts: 254
Location: Jambudweepam
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Can some one tell me wha is a user-defined header? I have tried searching the IBM documentation and at MQ series.net. May be I am missing something. Could you please point me to the right document that contains these details?
I was under the impression that "user defined header" was part of the variable part in MQRFH2 heder of a JMS message. Is that right?
| Quote: |
Variable portion
The variable portion follows the fixed portion. The variable portion contains a variable number of MQRFH2 folders. Each folder contains a variable number of elements or properties. Folders group together related properties. The MQRFH2 headers created by JMS can contain up to three folders:
The <mcd> folder
This contains properties that describe the shape or format of the message. For example, the Msd property identifies the message as being Text, Bytes, Stream, Map, Object, or null. This folder is always present in a JMS MQRFH2.
The <jms> folder
This is used to transport JMS header fields, and JMSX properties that cannot be fully expressed in the MQMD. This folder is always present in a JMS MQRFH2.
The <usr> folder
This is used to transport any application-defined properties associated with the message. This folder is present only if the application has set some application-defined properties.
The <mqext> folder
This is used to transport IBM® defined properties that are used only by WebSphere Application Server. This folder is present only if the application has set at least one of these properties
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I was thinking that the user defined header is The <usr> folder. Please let me know what is a "user-defined" header as regards to MQ |
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| Vitor |
| Posted: Mon Oct 05, 2009 4:31 pm Post subject: Re: User-defined header |
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Grand High Poobah
Joined: 11 Nov 2005
Posts: 26093
Location: Texas, USA
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| anveshita wrote: |
| I was thinking that the user defined header is The <usr> folder. |
It's clearly not a header per se, but it is a good place to put user defined values.
| anveshita wrote: |
| Please let me know what is a "user-defined" header as regards to MQ |
Remember that WMQ doesn't look at the structure of anything past the MQMD so a user defined header is anything which the application has placed in the payload which the application doesn't consider data.
A better question is where have you seen this term, and what do you plan to use such a header for?
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| PeterPotkay |
| Posted: Mon Oct 05, 2009 4:50 pm Post subject: Re: User-defined header |
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Poobah
Joined: 15 May 2001
Posts: 7722
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| Vitor wrote: |
| Remember that WMQ doesn't look at the structure of anything past the MQMD so a user defined header is anything which the application has placed in the payload which the application doesn't consider data. |
The format field of the MQMD may tell MQ that there are one or more headers (DLH, IIH, XMIT, etc) in the buffer, in which case MQ will be looking past the MQMD.
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Peter Potkay
Keep Calm and MQ On |
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| Vitor |
| Posted: Mon Oct 05, 2009 4:53 pm Post subject: Re: User-defined header |
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Grand High Poobah
Joined: 11 Nov 2005
Posts: 26093
Location: Texas, USA
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| PeterPotkay wrote: |
| The format field of the MQMD may tell MQ that there are one or more headers (DLH, IIH, XMIT, etc) in the buffer, in which case MQ will be looking past the MQMD. |
I thought the additonal headers were added to the front of the message? 
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| gbaddeley |
| Posted: Mon Oct 05, 2009 5:06 pm Post subject: |
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Jedi Knight
Joined: 25 Mar 2003
Posts: 2538
Location: Melbourne, Australia
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A MQRFH header can be used to define structured name / value pairs, but they are a bit messy to implement in most programming languages.
A user defined header is invented by the user in a similar format to well known MQ headers (StuctId, Version, Length, CCSID fields etc) but it will be ignored by MQ. MQ won't be able to parse, skip over, or convert it.
These days, user defined MQ headers or structures are best implemented using XML in the MQ Message Data, or stored in MQ Message Properties (new feature in v7.0).
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Glenn |
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| bruce2359 |
| Posted: Mon Oct 05, 2009 6:18 pm Post subject: |
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Poobah
Joined: 05 Jan 2008
Posts: 9472
Location: US: west coast, almost. Otherwise, enroute.
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Yay for Message Properties!
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| PeterPotkay |
| Posted: Mon Oct 05, 2009 6:33 pm Post subject: Re: User-defined header |
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Poobah
Joined: 15 May 2001
Posts: 7722
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| Vitor wrote: |
| PeterPotkay wrote: |
| The format field of the MQMD may tell MQ that there are one or more headers (DLH, IIH, XMIT, etc) in the buffer, in which case MQ will be looking past the MQMD. |
I thought the additonal headers were added to the front of the message? |
They are in front of the application data, but outside of the MQMD.
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Peter Potkay
Keep Calm and MQ On |
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| mqjeff |
| Posted: Tue Oct 06, 2009 1:12 am Post subject: |
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Grand Master
Joined: 25 Jun 2008
Posts: 17447
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| bruce2359 wrote: |
| Yay for Message Properties! |
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| Vitor |
| Posted: Tue Oct 06, 2009 7:21 am Post subject: Re: User-defined header |
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Grand High Poobah
Joined: 11 Nov 2005
Posts: 26093
Location: Texas, USA
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| PeterPotkay wrote: |
| Vitor wrote: |
| PeterPotkay wrote: |
| The format field of the MQMD may tell MQ that there are one or more headers (DLH, IIH, XMIT, etc) in the buffer, in which case MQ will be looking past the MQMD. |
I thought the additonal headers were added to the front of the message? |
They are in front of the application data, but outside of the MQMD. |
Yes, I thought they were in front of the original MQMD, i.e prepended to the original message.
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| bruce2359 |
| Posted: Tue Oct 06, 2009 7:32 am Post subject: |
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Poobah
Joined: 05 Jan 2008
Posts: 9472
Location: US: west coast, almost. Otherwise, enroute.
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IMS...
What ends up being send from a transmission queue consists of a new MQMD, followed by XQH, follwed by original MQMD, followed by application payload.
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Lex Orandi, Lex Credendi, Lex Vivendi. As we Worship, So we Believe, So we Live. |
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| Vitor |
| Posted: Tue Oct 06, 2009 7:39 am Post subject: |
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Grand High Poobah
Joined: 11 Nov 2005
Posts: 26093
Location: Texas, USA
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| bruce2359 wrote: |
IMS...
What ends up being send from a transmission queue consists of a new MQMD, followed by XQH, follwed by original MQMD, followed by application payload. |
I thought that.
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Honesty is the best policy.
Insanity is the best defence. |
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| bruce2359 |
| Posted: Tue Oct 06, 2009 8:01 am Post subject: |
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Poobah
Joined: 05 Jan 2008
Posts: 9472
Location: US: west coast, almost. Otherwise, enroute.
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I believe a msg in the dead-letter queue is similarly composed - new MQMD, DLH, original MQMD, app data.
_________________
I like deadlines. I like to wave as they pass by.
ב''ה
Lex Orandi, Lex Credendi, Lex Vivendi. As we Worship, So we Believe, So we Live. |
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| Vitor |
| Posted: Tue Oct 06, 2009 8:02 am Post subject: |
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Grand High Poobah
Joined: 11 Nov 2005
Posts: 26093
Location: Texas, USA
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| bruce2359 wrote: |
| I believe a msg in the dead-letter queue is similarly composed - new MQMD, DLH, original MQMD, app data. |
I thought that too.
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Honesty is the best policy.
Insanity is the best defence. |
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| gbaddeley |
| Posted: Tue Oct 06, 2009 4:57 pm Post subject: |
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Jedi Knight
Joined: 25 Mar 2003
Posts: 2538
Location: Melbourne, Australia
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| bruce2359 wrote: |
| I believe a msg in the dead-letter queue is similarly composed - new MQMD, DLH, original MQMD, app data. |
The Message Descriptor (MQMD) of a MQ message is not part of the Message Data payload, so it does not come before or after anything in the Message Data, it is separate. ie. the Message Data for a message on a DLQ consists of DLH, original MQMD, app data.
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Glenn |
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