Here is a situation: An application is running, It reads a Q or 2 writes a Q or 2 all in a UOW and the QMGR goes down now part of that UOW is a PUT to a queue prior to the MQCOMIT to ICE the processing deal. Are the messages comitted when the QMGR comes back up? Mr Diwakar never said he was in the middle of a MQCOMIT or MQBACK he just said "BEFORE" they were comitted. Granted if you issue a MQCOMIT/MQBACK this may or may not be the case but what are the implications when the QMGR takes a holiday in the middle of your processing (not necessarly in the middle of a direct communication with him/her).
bobbee
From: John Scott <[EMAIL PROTECTED]> Reply-To: MQSeries List <[EMAIL PROTECTED]> To: [EMAIL PROTECTED] Subject: Re: MQ behaviour - persistent messages availability when the qmgr crashes Date: Fri, 30 May 2003 17:10:19 -0000
I think there's a subtle "middlepoint" here.
You may not have received an RC=0 on the commit, but the messages may have been committed anyway. There would be a small window of opportunity where MQ has completed the commit, but before it could return RC=0 to the app, it all goes pear shaped.
I think the only guarantee is that either all the messages in the UOW will be committed or all will be backed out. You will never be able to get a situation where some of the messages in a UOW get committed and other in the same UOW get backed out.
I've seen other threads talking about this with respect to MQClient and to quote Paul Clarke:
"The semantics of messaging is exactly the same for a client as for a locally connected application. In other words, in order to do reliable messaging in a local application you must follow a certain set of rules like issuing MQPUTs and MQGETs under transactions etc. These rules are exactly the same for a client. One area which often concerns programmers is the MQCMIT call. What happens if you lose your network half way through an MQCMIT verb and get a MQRC_CONNECTION_BROKEN reason code. Did the transaction commit or didn't it ? Well, this is the same for a local application, you are not guaranteed to get a definitive answer on your transaction commit even for the local application. If you really care, you must do some 'known' action (like put a message to a queue) that you can subsequently check the next time you connect."
Regards John.
-----Original Message----- From: Robert Broderick [mailto:[EMAIL PROTECTED] Sent: 30 May 2003 15:28 To: [EMAIL PROTECTED] Subject: Re: MQ behaviour - persistent messages availability when the qmgr crashes
If you application didn't receive the RC=0 I believe it would be considered an inflight transaction and would be backed out upon QMGR restart.
>From: Diwakar S Yammanuru <[EMAIL PROTECTED]> >Reply-To: MQSeries List <[EMAIL PROTECTED]> >To: [EMAIL PROTECTED] >Subject: MQ behaviour - persistent messages availability when the qmgr > crashes >Date: Fri, 30 May 2003 10:58:39 -0400 > >Hello there. >When an application puts a persistent msg on a queue and if the >corresponding qmgr fails before the messge is committed/backed out >..... can the message still be recovered after the qmgr comes up ? I >mean, is the message logged ? > >Does a qmgr perform a commit/backout just before it crashes, if it is >the transaction manager ? > >Forgive me if the questions sound silly. > >thnx. >Diwakar. > > > >American Express made the following > annotations on 05/30/2003 07:58:49 AM >----------------------------------------------------------------------- >------- >*************************************************************************** *** > > "This message and any attachments are solely for the intended >recipient and may contain confidential or privileged information. If >you are not the intended recipient, any disclosure, copying, use, or >distribution of the information included in this message and any >attachments is prohibited. If you have received this communication in >error, please notify us by reply e-mail and immediately and permanently >delete this message and any attachments. Thank you." > >*********************************************************************** >******* > > >======================================================================= >======= > >Instructions for managing your mailing list subscription are provided >in the Listserv General Users Guide available at http://www.lsoft.com >Archive: http://vm.akh-wien.ac.at/MQSeries.archive
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