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| rammer |
 Posted: Wed Apr 21, 2004 1:49 am Post subject: MQMD |
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Partisan
Joined: 02 May 2002
Posts: 359
Location: England
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Hi
I have a general question regarding the size of the MQMD. Does anybody know if there is a default size of MQMD or does it depend on what context is added.
I have tried searching for the answer within this forum and through the MQ Application Programming Reference with out any luck.
Thank you in advance |
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| Michael Dag |
| Posted: Wed Apr 21, 2004 3:04 am Post subject: |
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Jedi Knight
Joined: 13 Jun 2002
Posts: 2607
Location: The Netherlands (Amsterdam)
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it's fixed length, if my memory serves me correctly 758 bytes in total.
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Michael
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| rammer |
| Posted: Tue Apr 27, 2004 12:49 am Post subject: |
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Partisan
Joined: 02 May 2002
Posts: 359
Location: England
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| Thanks for the prmpt reply. |
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| kman |
| Posted: Tue Apr 27, 2004 2:29 am Post subject: |
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Partisan
Joined: 21 Jan 2003
Posts: 309
Location: Kuala Lumpur, Malaysia
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| mmm is that really? I thought 4k is reserved for MQMD. Or was it 4k reserved for MQ headers.. so it should be MQMD + ? |
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| Michael Dag |
| Posted: Tue Apr 27, 2004 2:53 am Post subject: |
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Jedi Knight
Joined: 13 Jun 2002
Posts: 2607
Location: The Netherlands (Amsterdam)
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as far as I know the only part that is fixed and is reserved is the MQMD itself, any other header is 'technically' part of the 'payload' (and thus not reserved).
Whether 758 bytes is still valid or wether my memory is scrambled I wouldn't know 
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Michael
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| mqonnet |
| Posted: Tue Apr 27, 2004 4:45 am Post subject: |
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Grand Master
Joined: 18 Feb 2002
Posts: 1114
Location: Boston, Ma, Usa.
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You could add up all the field's sizes in the MQMD structure and you would get the length. Remember that if you dont include V2 fields, it would be different.
Just out curiosity though, why do you need it. I havent come accross a situation where i needed this info, since its an MQ internal structure.
Cheers
Kumar |
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| rammer |
| Posted: Tue Apr 27, 2004 5:43 am Post subject: |
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Partisan
Joined: 02 May 2002
Posts: 359
Location: England
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To be honest I am not sure why it is needed but one of our developers was after the figure.  |
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| mqonnet |
| Posted: Tue Apr 27, 2004 5:46 am Post subject: |
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Grand Master
Joined: 18 Feb 2002
Posts: 1114
Location: Boston, Ma, Usa.
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The only purpose i could think of is memory management. But since this is almost a neglegible amuont, its really not worth the time and effort digging into it. :)
Cheers
Kumar |
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| Michael Dag |
| Posted: Tue Apr 27, 2004 6:09 am Post subject: |
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Jedi Knight
Joined: 13 Jun 2002
Posts: 2607
Location: The Netherlands (Amsterdam)
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the reason I know about it is once we got bitten by it where an interface
between individual checkout machines in a supermarket was developed and
they were sending line item per line item in an MQ message,
the header / payload overhead turned out to be 5000% ... (sending 15 bytes with a 758 bytes header...)
clearly in some cases it is important information for your design ... 
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Michael
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| PeterPotkay |
| Posted: Tue Apr 27, 2004 10:14 am Post subject: |
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Poobah
Joined: 15 May 2001
Posts: 7722
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A Version1 MQMD is 364 bytes. I had to define a hold field in WorkIng Storage in a COBOL copybook to save off the original MQMD, and that was the length it turned out to be.
A Version2 MQMD would be a little longer.
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Peter Potkay
Keep Calm and MQ On |
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| Michael Dag |
| Posted: Tue Apr 27, 2004 12:24 pm Post subject: |
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Jedi Knight
Joined: 13 Jun 2002
Posts: 2607
Location: The Netherlands (Amsterdam)
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Can anyone verify the length of a Version2 MQMD,
otherwise I need to stop by the shop tomorrow first thing for some new memory blocks ... 
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Michael
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| PeterPotkay |
| Posted: Tue Apr 27, 2004 12:30 pm Post subject: |
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Poobah
Joined: 15 May 2001
Posts: 7722
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Michael, looking at the COBOL declaration of the Version 2 fields, I see an extra 40 bytes:
GroupID = 24 bytes
MsgSeqNumber = 4 bytes
OffSet = 4 bytes
MsgFlags = 4 bytes
OriginalLength = 4 bytes.
Maybe you were also factoring in the Transmit Queue Header, as well as TCP/IP "stuff" associatted with each MQ message?
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Peter Potkay
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| Michael Dag |
| Posted: Tue Apr 27, 2004 12:36 pm Post subject: |
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Jedi Knight
Joined: 13 Jun 2002
Posts: 2607
Location: The Netherlands (Amsterdam)
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758 - 364 - 40 = 354... could this indeed be the transmissionQ header?
the data was sent to another Qmgr at the time...
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Michael
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| kirani |
| Posted: Tue Apr 27, 2004 10:28 pm Post subject: |
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Jedi Knight
Joined: 05 Sep 2001
Posts: 3779
Location: Torrance, CA, USA
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Now I am getting confused! I believe the MQMD V2 size is 364 bytes.
| Code: |
struct tagMQMD {
MQCHAR4 StrucId; /* Structure identifier */
MQLONG Version; /* Structure version number */
MQLONG Report; /* Options for report messages */
MQLONG MsgType; /* Message type */
MQLONG Expiry; /* Message lifetime */
MQLONG Feedback; /* Feedback or reason code */
MQLONG Encoding; /* Numeric encoding of message data */
MQLONG CodedCharSetId; /* Character set identifier of message
data */
MQCHAR8 Format; /* Format name of message data */
MQLONG Priority; /* Message priority */
MQLONG Persistence; /* Message persistence */
MQBYTE24 MsgId; /* Message identifier */
MQBYTE24 CorrelId; /* Correlation identifier */
MQLONG BackoutCount; /* Backout counter */
MQCHAR48 ReplyToQ; /* Name of reply queue */
MQCHAR48 ReplyToQMgr; /* Name of reply queue manager */
MQCHAR12 UserIdentifier; /* User identifier */
MQBYTE32 AccountingToken; /* Accounting token */
MQCHAR32 ApplIdentityData; /* Application data relating to
identity */
MQLONG PutApplType; /* Type of application that put the
message */
MQCHAR28 PutApplName; /* Name of application that put the
message */
MQCHAR8 PutDate; /* Date when message was put */
MQCHAR8 PutTime; /* Time when message was put */
MQCHAR4 ApplOriginData; /* Application data relating to
origin */
MQBYTE24 GroupId; /* Group identifier */
MQLONG MsgSeqNumber; /* Sequence number of logical message
within group */
MQLONG Offset; /* Offset of data in physical message
from start of logical message */
MQLONG MsgFlags; /* Message flags */
MQLONG OriginalLength; /* Length of original message */
};
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Kiran
IBM Cert. Solution Designer & System Administrator - WBIMB V5
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| Michael Dag |
| Posted: Tue Apr 27, 2004 11:25 pm Post subject: |
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Jedi Knight
Joined: 13 Jun 2002
Posts: 2607
Location: The Netherlands (Amsterdam)
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well worth finding out what's the truth! (beats answering 2035 error questions )
So MQMD V2 = 364
TransmissinQ Header adds:
| Code: |
MQCHAR4 StrucId; /* Structure identifier */
MQLONG Version; /* Structure version number */
MQCHAR48 RemoteQName; /* Name of destination queue */
MQCHAR48 RemoteQMgrName; /* Name of destination queue manager */ |
4 + ??? + 48 + 48 = 100 + ???
how long is an MQLONG? (I am not a programmer obviously...)
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