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| fast channel v.s standard channel |
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| mqquester |
 Posted: Sat Nov 29, 2003 5:39 pm Post subject: fast channel v.s standard channel |
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Apprentice
Joined: 27 Nov 2003
Posts: 35
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Hi buddy,
Is fast channel used for non-persistant message, and standard channel can be used for non-persistant and persistant messages? Any message cannot be recovered through fast channel if there is any disaster?
I know fast channel of course has a faster speed. What else difference between them? Does anybody have a summary for them?
Best Regards,
mqquester |
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| PeterPotkay |
| Posted: Sat Nov 29, 2003 6:29 pm Post subject: |
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Poobah
Joined: 15 May 2001
Posts: 7722
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Both channels are just as fast, and you can send both Persistent (P) and Non-Persistent (NP) over either channel.
The difference is in how they handle NP messages. On a FAST channel NP messages are sent fire-and-forget. The sending MCA does not wait for a confirmation reply message from the receiving MCA. If there is a network blip, your NP message is lost. On a normal channel, the message would not be lost.
On a normal channel, the MCA's write info (persistent "logging-type" messages to a queue) to keep track of all messages, both P and NP. On a fast channel, there is no write for NP messages.
On a fast channel, the sending MCA will send the NP as soon as it gets it, and it does this outside of syncpoint, so the message is immediatly available on the other side.
Contrast this to a normal channel, where the both P and NP messages are put under syncpoint. That NP message will still be sent over to the other side just as fast as a FAST channel, but in this case the message will not be made available until the sending MCA issues a commit, which will happen based on the BATCHINT and BATCHCOUNT setting.
In most cases, there is no performance diff in setting your channel to NORMAL, but you get the benifit of never losing NP messages.
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Peter Potkay
Keep Calm and MQ On |
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| mqquester |
| Posted: Sun Nov 30, 2003 2:54 pm Post subject: |
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Apprentice
Joined: 27 Nov 2003
Posts: 35
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Hi Peter,
From your article, it looks for normal channel, the P and NP messages are same. The NP message will not be lost even if there is a network problem.
I thought NP message will be lost if there is a problem between transfer not only for fast but normal channel as well. Am I wrong?
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| PeterPotkay |
| Posted: Sun Nov 30, 2003 3:21 pm Post subject: |
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Poobah
Joined: 15 May 2001
Posts: 7722
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NP messages will not be lost in flight if there is a network problem and the channel speed is NORMAL.
NP messages will be lost if they are sitting in a queue and the queue manager goes down, for whatever reason. Once the QM comes back up, NP messages are gone.
When determining whether a message should be persistent or not, the ONLY criteria is whether you want the message to survive a QM restart if it was sitting in a queue.
If you are concerned about NP messages being lost in a channel, the solution is channel speed (set it to NORMAL), not the persistence of the message. Setting a message to persitent just for this reason is overkill as you incur all the overhead of disk writes as the message is written to logs every step of the way. Yes, it will get you the same end result (the message is not lost over a channel), but it is not the right way to do it.
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Peter Potkay
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| mqquester |
| Posted: Mon Dec 01, 2003 7:28 am Post subject: |
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Apprentice
Joined: 27 Nov 2003
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