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| Problem in MQDLQ in the MA10 support pack |
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| tleichen |
 Posted: Thu Jan 27, 2011 6:56 am Post subject: Problem in MQDLQ in the MA10 support pack |
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Yatiri
Joined: 11 Apr 2005
Posts: 663
Location: Center of the USA
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The source for module MQDLQ0 is a Cobol program. The documentation in the source states the following:
MODIFICATIONS:
FIXED GETMAIN PROBLEM FOR LARGE VALUES FOR "GO"
FIXED PROBLEM WITH GO 1
However, this does not appear to be the case. Also, I can type "GO 1000" once and not get an error, but doing it a second time yields the following:
IEW4000I FETCH FOR MODULE IGZINSH FROM DDNAME -LNKLST- FAILED BECAUSE INSUFFICIENT STORAGE WAS AVAILABLE.
CSV031I LIBRARY ACCESS FAILED FOR MODULE IGZINSH , RETURN CODE 24, REASON CODE 26080021, DDNAME *LNKLST*
IEW4000I FETCH FOR MODULE IGZCMGEN FROM DDNAME -LNKLST- FAILED BECAUSE INSUFFICIENT STORAGE WAS AVAILABLE.
CSV031I LIBRARY ACCESS FAILED FOR MODULE IGZCMGEN, RETURN CODE 24, REASON CODE 26080021, DDNAME *LNKLST*
CEE3798I ATTEMPTING TO TAKE A DUMP FOR ABEND U4087 TO DATA SET: XXXXXXX.Dddd.Thhmmsst.XXXXXXX
The ISPF session abends with a S0C4. In looking at the code, it appears that it is doing a call to MEMGET every time it does an MQGET. This appears to be the last modification to the source, but it did not fix what it said it did. I have tried rebuilding the module, but the results are the same. Has anyone else fixed this problem? 
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| Mr Butcher |
| Posted: Fri Jan 28, 2011 12:04 am Post subject: |
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Padawan
Joined: 23 May 2005
Posts: 1716
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The problem is, that the go command is implemented as a browse from the beginning of the queue in a loop till the message number specified on the go command is reached. That loop calls 1300-get-message which issues a getmain, regardless if this message is just skipped during the browse or not.
I solved it by adding a flag and performing the getmain only once in the loop (for the first message). This reduces the number of getmains so also a large "go" can be handled. Other solution may be possible, e.g. setting length to 0 during the browse but i did not check if that would result in a 0 byte getmain.
However, i did not check for missing freemains.
In addition, if i have a large number of messages in my DLQ, i check the first ones for the reason and then run the dlq handler. Then i check what remains. In most cases 1 run is sufficient as theres only 1 error and all DLQ messages hold the same reason code (my DLQ is empty otherwise).
In test environment i used to have many and old messages in the DLQ because nobody cared and nobody checked. One day I implemented an automatic DLQ notify process, that notifies developement about DLQ messages by email including a dump of the first xx messages, and moves messages to specific queues adding message expiry.
So in test environment i do not have to perform any manual actions on the DLQ ..... but well, i recognize i am off toppic ....
So here is my code.
| Code: |
in the WSS
..
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05 WS-GO-FLAG PIC X VALUE SPACE.
88 WS-GO VALUE 'Y'.
88 WS-GO-END VALUE 'N'.
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in the Procedure Division
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0000-MAINLINE SECTION.
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IF WS-CMD-PART1 = 'GO'
IF WS-CMD-PART2 IS NUMERIC
MOVE MQGMO-BROWSE-FIRST TO WS-OPTIONS
MOVE 0 TO WS-NMR
PERFORM 1200-OPEN-DEADQ
PERFORM 1300-GET-MESSAGE
MOVE MQGMO-BROWSE-NEXT TO WS-OPTIONS
SUBTRACT 1 FROM WS-CMD-PART2
* Indicate GO command
SET WS-GO TO TRUE
*
PERFORM 1300-GET-MESSAGE
WS-CMD-PART2 TIMES
* switch off GO command
SET WS-GO-END TO TRUE
*
PERFORM 1400-FORMAT
END-IF
..
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1300-GET-MESSAGE.
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ADD MQGMO-ACCEPT-TRUNCATED-MSG TO MQGMO-OPTIONS.
ADD MQGMO-FAIL-IF-QUIESCING TO MQGMO-OPTIONS.
IF NOT WS-GO
* no GETMAIN as records are only skipped
MOVE WS-SIZE TO WS-BUFFLEN
CALL WS-GETMAIN USING WS-SIZE
WS-ABOVE
WS-BUFFER-PTR
SET ADDRESS OF LS-BUFFER TO WS-BUFFER-PTR
END-IF.
ADD 1 TO WS-NMR.
PERFORM 2200-MQGET.
..
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| tleichen |
| Posted: Wed Feb 02, 2011 2:17 pm Post subject: |
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Yatiri
Joined: 11 Apr 2005
Posts: 663
Location: Center of the USA
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Thanks. That method solves the problem of superfluous getmains!
Another oddity that I see now is that if the messages in the DLQ are different sizes, the display buffer does not get cleared and/or the buffer size gets corrupted with multiple GO commands. For example, I have 3 messages and their lengths are 20, 40, and 30. If I type:
GO 1
GO 2
GO 3
then the buffer displays the 30 characters of the third record followed by the last 10 of the second record.
But, if I type
GO 1
<enter>
<enter>
The display works properly. Logically, this should be identical.
I've perused the source trying to find what was missed, but it's eluding me.
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| fjb_saper |
| Posted: Wed Feb 02, 2011 8:16 pm Post subject: |
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Grand High Poobah
Joined: 18 Nov 2003
Posts: 20756
Location: LI,NY
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| tleichen wrote: |
Thanks. That method solves the problem of superfluous getmains!
Another oddity that I see now is that if the messages in the DLQ are different sizes, the display buffer does not get cleared and/or the buffer size gets corrupted with multiple GO commands. For example, I have 3 messages and their lengths are 20, 40, and 30. If I type:
GO 1
GO 2
GO 3
then the buffer displays the 30 characters of the third record followed by the last 10 of the second record.
But, if I type
GO 1
<enter>
<enter>
The display works properly. Logically, this should be identical.
I've perused the source trying to find what was missed, but it's eluding me. |
Looks to me like the problem could have 2 origins:
a) the buffer is not initialized between 2 get calls
b) As the size of the buffer is not changed, when the message size is less than the buffer size, the full buffer size is still being passed for display. You need to make sure that you are reading/showing only the max of buffersize / messagesize...
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| Mr Butcher |
| Posted: Mon Feb 07, 2011 4:15 am Post subject: |
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Padawan
Joined: 23 May 2005
Posts: 1716
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why do you care for the message content? this is not a queue browser. its a dlq handler. for me, the most important information is the one that is hold in the DLH, e.g. the reason code why the messages is on the DLQ and the related object names. Then i know what the problem is and can go and solve it or run the DLQ handler.
If you want to browse, use suggest to use a different tool.
Although i agree with you that it is not coded very well ..... but... well.. supplied as it is .. to verify your cobol skills 
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| mqjeff |
| Posted: Mon Feb 07, 2011 5:12 am Post subject: |
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Grand Master
Joined: 25 Jun 2008
Posts: 17447
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So the buffer is reused but not cleared between gets.
Not so hard to MOVE SPACES is it? |
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| Mr Butcher |
| Posted: Mon Feb 07, 2011 6:02 am Post subject: |
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Padawan
Joined: 23 May 2005
Posts: 1716
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well, it depends 
| Code: |
IF NOT WS-GO
MOVE WS-SIZE TO WS-BUFFLEN
CALL WS-GETMAIN USING WS-SIZE
WS-ABOVE
WS-BUFFER-PTR
SET ADDRESS OF LS-BUFFER TO WS-BUFFER-PTR
ELSE
MOVE SPACES TO LS-BUFFER
END-IF. [ |
not that performant as it does the move spaces for every message that is skipped. but its quick and dirty (and so fits into this program).
other solution for cobol learners - split the n time loop fopr the go into
n-1, then move spaces, then call the final mqget. but i was not in the mood for that.
however, please recognise that the maximum message length the program will handle is 32k
| Code: |
ADD LENGTH OF MQDLH TO 32767 GIVING WS-SIZE
MOVE 32767 TO WS-MSG-SIZE |
thats why it reads using accept truncated message.
so, again, if for browsing, use something different
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