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| Is it ok to start a channel to get it out of retrying state? |
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| egoine |
 Posted: Wed Apr 17, 2002 11:54 am Post subject: |
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Newbie
Joined: 16 Apr 2002
Posts: 6
Location: Montreal
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Hi all,
Just want to make sure I understand things correctly.
We have machine A (queue manager A) that talks via channel C to machine B(queue manager B).
Sometimes, machine B goes down for planned maintenance. When this occurs, I'm switching to sending messages to a second machine B2 instead of B via another channel.
Then the channel C on machine A goes into retrying state.
Now when machines B comes back, I am sending a special message to machine A telling that it is up again. I then use the PCF Java API and code from a old MQ Update article (both of which I've found references in these forums) to send a "start" to the channel C. I do this to ensure the channel is back up, before starting to send messages again. This is because I noticed (and read in the documentation) that the retrying is done with a certain interval and the channel C will not come back up as soon as machine B comes back up. All of this is automated (i.e. programmatic).
Now, I guess there is a lot of different ways of doing all of this, like using clustering, but my real question is :
Does what I described above make sense? Any big mistake?
Also, from my observations, sending a "start" to an already started channel does not cause trouble.
thanks |
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| bduncan |
| Posted: Wed Apr 17, 2002 4:37 pm Post subject: |
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Padawan
Joined: 11 Apr 2001
Posts: 1554
Location: Silicon Valley
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Your method will work, just consider the following point. Sometimes channels are in RETRY mode for reasons other than network connectivity issues. In these cases, you can get the sequence numbers for the channel out of sync. Simply issuing a start command to a channel such as this will not get it running again. It will stay in retry mode until the discrepancy is resolved, usually by manual intervention, by issuing the RESET CHANNEL command and setting the sequence number to either the number you think it should be, or 1 (if you don't know what it should be).
So in your case, if you take the queue manager down right when another queue manager is sending a message to it, this message may remain in limbo after the queue manager comes back online. Because the sender side thinks the sequence number is x+1 (since it sent the message on its merry way, but hasn't gotten a confirmation of delivery yet) and the receiver side still thinks the sequence number is x, then you need to issue a reset command on the sender side before you can successfully restart the channel.
But if you can protect against these situations arising, then your program should be able to restart the channels. Also, if the channel is already running it does no harm to issue another start command...
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Brandon Duncan
IBM Certified MQSeries Specialist
MQSeries.net forum moderator |
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| egoine |
| Posted: Thu Apr 18, 2002 7:40 am Post subject: |
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Newbie
Joined: 16 Apr 2002
Posts: 6
Location: Montreal
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Hi!
thanks a lot for the fast and professionnal response. Is there a place where I can "tip" this site, or you (let's say with paypal)?
Know any good links or the ibm pdf I should read regarding the case you mentionned (sequence numbers and loosing a message in limbo). I'm confused by all the PDF files, since their filename isn't really helpfull (csqzax00.pdf??). |
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| PeterPotkay |
| Posted: Thu Apr 18, 2002 8:12 am Post subject: |
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Poobah
Joined: 15 May 2001
Posts: 7722
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| bduncan |
| Posted: Fri Apr 19, 2002 10:40 am Post subject: |
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Padawan
Joined: 11 Apr 2001
Posts: 1554
Location: Silicon Valley
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egoine,
Thank you for the offer. I by no means want to solicite anything from the members of this site, but as you can imagine, I do have expenses related to the running of this site (especially the T1 it's running on!). I host the site myself rather than through some service in order to have more control over the maintenance, etc., of the site. So if you (or anyone else) do wish to make a contribution to the continued upkeep of the site, I'd greatly appreciate it, but again, even if nobody ever gives me a penny, the site will continue to run for the forseeable future. If you are still interested, and no amount will be too small; of course, it'll be more than anyone has ever given before! 
You can send contributions to my paypal account which is under my email address, bduncan@mqseries.net
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Brandon Duncan
IBM Certified MQSeries Specialist
MQSeries.net forum moderator |
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