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Two phase commit

 
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Pandora-Box

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PostPosted: Sun Mar 25, 2012 9:35 pm    Post subject: Two phase commit
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Hi all,

I have three programs A,B,C

A ==> Main driver cics program which links B and calls C dynamically
B ==> CICS program which process data in tables
C ==> MQ routine which would be called for every MQ operation ( open,put,close)

Now the major driver CICS program A does some process and links B and inserts some records to tables

The program B actually does "EXEC CICS SYNCPOINT END-EXEC" if SQLCODE of table process is 0

So My table has data like

Code:
PROGRAM STARTED
PROGRAM FIRST HALF WITHOUT ERRORS

"The records are actually commited"

and later it calls program C and suppose if open of MQ fails I again link
program B and try to process the tables and the table process was successful and returns back to A where since the MQ process failed I do a SYNCPOINT ROLLBACK

As a table record I try inserting

Code:
MQ PROCESS FAILED


"The records inserted after calling MQ program has not commited"

So its like

My table at the end it has data

Code:
PROGRAM STARTED
PROGRAM FIRST HALF WITHOUT ERRORS


I have two questions here

1.If my first set of records are actually inserted before MQ program call why didnt it insert a record after MQ failure when data insertion was succesful

2.SYNCPOINT ROLLBACK should rollback all the data till the previous syncpoint why didnt it happen that way??

If my doubts are wrong I guess there is some serious problems with my understanding icon_redface.gif

Could someone please help me out??
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dbzTHEdinosauer

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Joined: 20 Oct 2006
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Location: porcelain throne

PostPosted: Sun Mar 25, 2012 11:03 pm    Post subject:
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you should have the logic to do a syncpoint or rollback in the same place.

keep in mind, the idea of RRSAF
(where you have more than one resource,
in this case DB2 and MQS)
you want a 'commit' or 'rollback' decision based on 'unit of work'.

if the MQS write is based on a successful completion of DB2 process,
you should do the sycnpoint after the MQS write
and not
afer the DB2 process
otherwise, you have divided a unit-of-work, which you should not do.

now, as to your question about what is or is not there after commit and rollback,
insure that you are using RRSAF.

if you are not using RRSAF, then that is another conversation, for another time.

as to why you are performing what should be a batch process in cics,
let the fact that i made the comment suffice as a negative critique.

and last but not least, forget the fact that you have 3 programs,
IT IS ONE TASK,
and work is accomplished in a task, and not a program.
if it helps,
just think as the linked-to and CALLed program as just two more paragraphs within the mainmodule.
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Pandora-Box

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PostPosted: Sun Mar 25, 2012 11:22 pm    Post subject:
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Yes Dick

Thanks I understand your point but say there is a requirement that I need to inform certain users that MQ has been failed due to some reason may be like when MQs are down after DB2 process

Yes I do agree with you I need to consider things "1 Unit of work"

How to acheieve that??
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dbzTHEdinosauer

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PostPosted: Mon Mar 26, 2012 1:11 am    Post subject:
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you never answered my question about RRSAF.
the 1 unit of work decision is based on your answer to that.
Do you have it installed and implemented?

as far as as informing users that something is not available,
i prefer to notify those who are responsible for insuring that a service is available.
as to notifying the user, how are you communicating with them now?

i have no idea about what your process actually does.
is it screen driven by a user, where you have essentially one transaction?
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Pandora-Box

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PostPosted: Mon Mar 26, 2012 7:49 am    Post subject:
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Yes RRSAF is installed nd yeah one unit of work gets done after writing to MQ

No its,not a screen but a web page which calls A
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dbzTHEdinosauer

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PostPosted: Mon Mar 26, 2012 4:07 pm    Post subject:
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if the unit of work is complete when mqs is written,
then that is when the syncpoint should be taken either commit or rollback.

when then webpage invokes cics transaction,
how many db2 processes and mqs processes are expected for each invocation?

This thread:
http://ibmmainframes.com/about55525.html
last two post are of interest.
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Pandora-Box

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PostPosted: Tue Mar 27, 2012 12:24 am    Post subject:
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Yes RRSAF is installed nd yeah one unit of work gets done after writing to MQ

No its,not a screen but a web page which calls A
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dick scherrer

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Joined: 23 Nov 2006
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PostPosted: Wed Mar 28, 2012 3:19 am    Post subject: Reply to: Two phase commit
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Hello,

Was there some reason to re-post your previous reply?

I suspect it would have been more productive to answer the question from DBZ as well as comment on the link provided. . . icon_confused.gif

d
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Pandora-Box

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PostPosted: Wed Mar 28, 2012 10:02 am    Post subject:
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Oops Apologies my mistake I guess I am in need of break badly I never know why I replied that

For each webpage invocation. I process webpage atleast three times and write to MQ just once

I did see that link long back when the other Dick
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