bee-oh-dubble-bee-dubble-egh
From: Francois Van der Merwe1 <[EMAIL PROTECTED]> Reply-To: MQSeries List <[EMAIL PROTECTED]> To: [EMAIL PROTECTED] Subject: Re: SYNCPOINT behaviour Date: Tue, 7 Oct 2003 17:42:07 +0200
Hi Everybody The original poster of this question again. Thanks for all the responses etc. From time to time I help our training guys out and then I give some of the MQ training classes. For one, it breaks my routine a little bit, I learn to know my customers a little better and it gives me a chance to see if there is anything new in the training manuals. And then sometimes I actually prepare for the class and even try out some of the new things.
In the latest MQ15 (MQ Admin I) training manuals (dated June 2003) there was this "one liner" stating that you can get a syncpoint message from the queue even before the commit only if done in the same UOW. Now I thought this was a mistake, so I whipped out my favourite C compiler and I changed amqsput0 a little bit to emulate that behaviour. And I must admit I was VERY surprised to see that it works exactly like that. So, the message was not available, but true, you can get it back in the same UOW.
I was still a bit sceptical, so that is why I posted the question to the group, just to see what the rest of you are saying, and as usual the group did not disappoint me! Great work guys!
So I do not know if it was always like that or if it was never in the training manual or if I just did not give any attention to it.... but presto, I learned something new!
Have fun!
Francois van der Merwe Senior IT Specialist: IBM MQSeries Certified Specialist, Solutions Expert & Developer IBM, Cape Town, South Africa +27 (0)82 556 9467 / +27 (0)21 402 5597 [EMAIL PROTECTED]
Robert Broderick <[EMAIL PROTECTED] To: [EMAIL PROTECTED] OTMAIL.COM> cc: Sent by: MQSeries Subject: Re: SYNCPOINT behaviour List <[EMAIL PROTECTED] .AC.AT>
07/10/2003 13:08 Please respond to MQSeries List
Yee of little faith!!!!!
>From: John Scott <[EMAIL PROTECTED]> >Reply-To: MQSeries List <[EMAIL PROTECTED]> >To: [EMAIL PROTECTED] >Subject: Re: SYNCPOINT behaviour >Date: Tue, 7 Oct 2003 08:53:46 -0000 > >I'll come clean and admit that I had to knock up a quick combination of >amqsput/amqsget to find out the real answer... > >Regards >John Scott >IBM Certified Specialist - MQSeries >Argos Ltd > > >-----Original Message----- >From: Neil Casey [mailto:[EMAIL PROTECTED] >Sent: 07 October 2003 03:32 >To: [EMAIL PROTECTED] >Subject: Re: SYNCPOINT behaviour > > >Hi Peter, > >your description matches my expectations (I replied earlier), but does not >match what Bobbee and John said. > >So, I fired up the MQ API excerciser to try it out. > >Sure enough, and to my complete surprise, the first MQGET (prior to the >commit) is able to return the message. After the first commit the queue is >empty again because the message has already been removed. I could not find >anywhere in the manuals that describes this behaviour, but it is what MQ >does. All the manual says is that a commit makes the message available to >OTHER threads. I guess you could read into that that the message is always >available in its own thread. That turns out to be the case anyway. > >So the question was not as straightforward as I assumed, and produced an >interesting learning experience, for me at least. > >Regards, > >Neil Casey. > > >|---------+------------------------------> >| | "Potkay, Peter M | >| | (PLC, IT)" | >| | <[EMAIL PROTECTED]| >| | RTFORD.COM> | >| | Sent by: MQSeries | >| | List | >| | <[EMAIL PROTECTED]| >| | AC.AT> | >| | | >| | | >| | 07/10/2003 12:00 | >| | Please respond to | >| | MQSeries List | >| | | >|---------+------------------------------> > > > --------------------------------------------------------------------------- >-----------------------------------| > | >| > | To: [EMAIL PROTECTED] >| > | cc: >| > | Subject: Re: SYNCPOINT behaviour >| > > > --------------------------------------------------------------------------- >-----------------------------------| > > > > >I assume Q1 is empty at this point. > > > > >empty buffer2 >buffer2 is empty > > > >Set text "MQ Rules" to buffer1 >buffer2 is empty > > > >Open Queue Q1 > > > >Set PutMessageOptions to PMO_SYNCPOINT > > > >Put buffer1 into Q1 >buffer2 is still empty, queue depth is increased by 1, message is not >available since it is not commited. > > > >Set GetMessageOptions to GMO_SYNCPOINT >buffer2 is empty > > > >Get into buffer2 from Q1 >buffer2 is empty, because the MQGET threw a 2033, as there were no >available >messages on the queue. > > > >Commit >buffer2 is empty, queue depth is still 1, but now the message is available. > > > >Get into buffer2 from Q1 >buffer2 contains a pearl of wisdom proclaiming that "MQ Rules". Bobbee >finally now knows what he wants his new tattoo to say. > > > >Commit > > > >end > >-----Original Message----- >From: Robert Broderick [mailto:[EMAIL PROTECTED] >Sent: Monday, October 06, 2003 4:22 PM >To: [EMAIL PROTECTED] >Subject: Re: SYNCPOINT behaviour > > >AAAAAAHHHHHHHH!!!!!!! > >I like your last sentence ....and was thinking that too.....but I thought >we >were being theoretical here!!!! (like when the kid asks his father the >difference between "Fantasy and Reality") > >I have noticed that we have not heard from the poster of this fine >question. >Are they sitting back giggling while me and you swing it out on a technical >intellectual level. (cause the person I'm paying to keep up my end has to >go >home and drink a beer!!!!! hahaha). > > > > > bobbee > >Now for something completely different. I have a OS390 broker that is >abending and the abend file, while not saying much, sez "SEMCTL". >Anybody??? > > > >From: John Scott <[EMAIL PROTECTED]> > >Reply-To: MQSeries List <[EMAIL PROTECTED]> > >To: [EMAIL PROTECTED] > >Subject: Re: SYNCPOINT behaviour > >Date: Mon, 6 Oct 2003 18:10:11 -0000 > > > >Putting shared handles aside for a second, the HCONN is only valid on > >the "smallest unit of execution" which in most cases is a thread rather > >than a process. > > > >So if you try multiple connects on the same thread, you'll get a > >MQRC_ALREADY_CONNECTED *warning*. However, the HCONN value returned > >will >be > >the same as the originally returned HCONN (2002 is a warning, not a > >failure). This would mean the same UOW and being able to get an >uncommitted > >put from the same UOW. On another thread, you get a different HCONN > >value returned. This would mean no getting of your uncommitted message. > > > >I am not 100% sure what would happen if you used shared handles (I've > >not actually tried them yet). I would expect that two separate HCONNs > >on the same thread would have two different units of work and so would > >operate >the > >same as two separate threads/processes with their own HCONNs. > > > >This is all assuming that the return codes from the calls indicate > >success and that the original code snippet had all the checking removed > >to easy readability - rather than having Francois post the entire > >amqsput/amqsget samples combined... > > > >The next question I have (well another guy in the office I asked) is > >why would you want to put a message under syncpoint and then get it > >again in the same UOW?? > > > >Regards > >John Scott > >IBM Certified Specialist - MQSeries > >Argos Ltd > > > >PS. What does TCB stand for? Is the an OS/390 thing? > > > > > >-----Original Message----- > >From: Robert Broderick [mailto:[EMAIL PROTECTED] > >Sent: 06 October 2003 16:29 > >To: [EMAIL PROTECTED] > >Subject: Re: SYNCPOINT behaviour > > > > > >Your right John, BUT....today I am a purest!!!!!!!! (and I know someone > >else would get to the point!!) > > > >Also, If you try to connect to a QMGR twice from inside the same > >task/process don't you get a return code indicating >"MQRC_ALREADY_CONNECTED > > 2002". So the alternate HCONN would have to be performed from > >another task/process. That then would follow the normal rules for >syncpoint > >processing > > > > > >bee-oh-dubble-bee-dubble-egh > > > > > > >From: John Scott <[EMAIL PROTECTED]> > > >Reply-To: MQSeries List <[EMAIL PROTECTED]> > > >To: [EMAIL PROTECTED] > > >Subject: Re: SYNCPOINT behaviour > > >Date: Mon, 6 Oct 2003 15:45:32 -0000 > > > > > >Isn't the fundamental question that Francois is asking is whether MQ > > >makes a message put under syncpoint available if an attempt to get > > >the message is performed within the SAME unit of work (i.e. before > > >the work is committed)? > > > > > >The answer is yes. Thus if you put a message under syncpoint, you can > > >get the message before a commit, if you use the same HCONN and > > >specify MQGMO_SYNCPOINT on your get. If you use another HCONN, or > > >don't use MQGMO_SYNCPOINT, then the message is not available. > > > > > >Regards > > >John Scott > > >IBM Certified Specialist - MQSeries > > >Argos Ltd > > > > > > > > >-----Original Message----- > > >From: Robert Broderick [mailto:[EMAIL PROTECTED] > > >Sent: 06 October 2003 13:24 > > >To: [EMAIL PROTECTED] > > >Subject: Re: SYNCPOINT behaviour > > > > > > > > >MQ Rules. What else!! > > > > > >Assume that the first MQGET works because your TCB actually owns the > > >message you are trying to get. (This may be the case as if IBM copied > > >the code correctly). BUT if it doesn't your second MQGET will > > >certainly fill up the buffer with the message that you put at the > > >start of the cde segment. Either way you will end up with "MQ Rules" > > >and you will not necessarlly know > >from > > >which MQGET it came from because you don't check codes and you do not > >clear > > >the buffer after the call. You could get a 2033 on the first MQGET > > >but wouldn't realize it. > > > > > > > > > bobbee > > > > > > > > > >From: Francois Van der Merwe1 <[EMAIL PROTECTED]> > > > >Reply-To: MQSeries List <[EMAIL PROTECTED]> > > > >To: [EMAIL PROTECTED] > > > >Subject: SYNCPOINT behaviour > > > >Date: Sat, 4 Oct 2003 13:06:45 +0200 > > > > > > > >What will be the value in the buffer2 in the following code just > > > >before the commit and at the end of the code segment. > > > > > > > >Empty Q1 > > > >Application A: (only application with access to Q1) > > > >.... > > > >empty buffer2 > > > >Set text "MQ Rules" to buffer1 > > > >Open Queue Q1 > > > >Set PutMessageOptions to PMO_SYNCPOINT > > > >Put buffer1 into Q1 > > > >Set GetMessageOptions to GMO_SYNCPOINT > > > >Get into buffer2 from Q1 > > > >Commit > > > >Get into buffer2 from Q1 > > > >Commit > > > >end > > > > > > > > > > > >Francois van der Merwe > > > > > > > >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 > > > > > >_________________________________________________________________ > > >Instant message with integrated webcam using MSN Messenger 6.0. 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