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| two phase commit for : z/OS, Cics, 3270 bridge, DB2, Cobol |
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| EgilsJ.Rubenis |
 Posted: Thu Jan 23, 2003 12:47 am Post subject: two phase commit for : z/OS, Cics, 3270 bridge, DB2, Cobol |
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Acolyte
Joined: 18 Nov 2002
Posts: 63
Location: Germany, Alfeld
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Hi,
can somebody tell me how to implement a two phase commit?
I have incoming messages on Queue triggering a CicsTransaction.
The CicsTransaction updates data in a DB2 table.
My assumption so far from what i read in books is:
CicsTransaction
EXEC CICS SYNCPOINT
PERFORM UNTIL NO FURTHER MESSAGES
MQGET
INSERT DATA on TABLE
COMMIT
Question: Does the Commit set both, the Message and the DB Changes
or ist there anything else to do ?
thanks for your help |
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| oz1ccg |
| Posted: Thu Jan 23, 2003 2:07 am Post subject: |
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Yatiri
Joined: 10 Feb 2002
Posts: 628
Location: Denmark
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In CICS, the CICS acts as two-phase Commit coordinator, and therefore demands the other resource managers to either do commit or backout. So twophase commit is done automaticly in CICS.
You control it with EXEC CICS SYNCPOINT or EXEC CICS SYNCPOINT ROLLBACK, this is all in the CICS Application Programming Reference manual.
I have a comment on your design:
I personally like to do commits often, so I don't get a deadlock, because many systems are on-line systems.
CicsTransaction
| Code: |
PERFORM UNTIL NO FURTHER MESSAGES
MQGET
INSERT DATA on TABLE
EXEC CICS SYNCPOINT
END-PERFORM
MQCLOSE |
The last MQCLOSE is important, (the manual say that CICS do it automaticly) because the CICS will first issue the MQCLOSE when it have resources for cleanup, or are in need of resources.
I had this situation:
The queue was open for input, and therefore didn't MQ issue a new trigger, and waited until eiter the triggerinterval occured or cleanup in the CICS.... Quite difficult to spot, because the CICS task was invisible in CEMT I TA(*)
Just my $0.02 
_________________
Regards, Jørgen
Home of BlockIP2, the last free MQ Security exit ver. 3.00
Cert. on WMQ, WBIMB, SWIFT.
Last edited by oz1ccg on Thu Jan 23, 2003 2:14 am; edited 1 time in total |
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| bob_buxton |
| Posted: Thu Jan 23, 2003 2:09 am Post subject: |
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Master
Joined: 23 Aug 2001
Posts: 266
Location: England
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You use the EXEC CICS SYNCPOINT to perform the commit so you would not do that call first. This will cause DB2, MQ and any other resource managers to commit their updates.
You could choose to issue the Syncpoint after performing the DB2 updates relating to a sungle MQ message, after a group of messages or after emptying the whole queue. If you choose the latter option you need to consider how long you might be holding locks on DB2 rows whilst processing the queue, especially if you use MQGET WAIT to wait for more messages to arrive on the queue.
_________________
Bob Buxton
Ex-Websphere MQ Development |
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