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MQSeries.net Forum IndexGeneral IBM MQ SupportIBM MQ MAXMSGL and performance

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aruncg
PostPosted: Thu Dec 07, 2017 6:38 am Post subject: IBM MQ MAXMSGL and performance Reply with quote

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Joined: 08 Mar 2013
Posts: 18

Hi,

We have an MQ (V8.0.0.4) system where Datapower publishes messages to MQ via a server connection channel. There are 2 subscriptions -1 which will eventually consumed by an AMQP client through an AMQP channel and another pushes messages to a remote queue manager via a remote queue. The transaction volume is quite high - it can reach upto 1000 msgs/sec an average transaction rate of around 500msgs/sec. Currently the maximum message length of the queue manager and channels are set as the default value( 4MB). Most of the messages are small ( less than 15KB) but there can be few messages (consider less than 100 per day ) which can have a maximum size of 16 MB. Currently messages which are greater than 4MB are failing due to the MAXMSGL limitation. If I increase the value of this attribute (Qmgr, Queue & channel ) to 16MB, then will it have any significant performance impact?


regards
cg
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bruce2359
PostPosted: Thu Dec 07, 2017 7:17 am Post subject: Re: IBM MQ MAXMSGL and performance Reply with quote

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Joined: 05 Jan 2008
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Location: US: west coast, almost. Otherwise, enroute.

aruncg wrote:
I increase the value of this attribute (Qmgr, Queue & channel ) to 16MB, then will it have any significant performance impact?

Yes and no.

Yes, it will allow your transactions with messages >4MB to complete successfully.

No, maximum msglength/queuedepth only set limits, but otherwise have little impact on performance.
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zpat
PostPosted: Thu Dec 07, 2017 7:22 am Post subject: Reply with quote

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Joined: 19 May 2001
Posts: 5579
Location: UK

Increasing the max message length would probably incur some extra memory buffer allocation.

Best thing would be to try it and see the effect (if any).
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Well, I don't think there is any question about it. It can only be attributable to human error. This sort of thing has cropped up before, and it has always been due to human error.
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fjb_saper
PostPosted: Thu Dec 07, 2017 10:35 am Post subject: Reply with quote

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Joined: 18 Nov 2003
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Location: LI,NY

From my experience with Java, I'd say bigger messages have definitely an impact on performance. Think of memory allocation and think of throughput.
Now if you think in matter of bytes per second, the throughput might essentially be only degraded by very little. If you think in messages per second, the degradation will be obvious.
It may take up to 2 seconds to load a big message into java memory..., a small one is loaded in a matter of milliseconds...

Have fun
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aruncg
PostPosted: Fri Dec 08, 2017 3:30 am Post subject: Reply with quote

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Joined: 08 Mar 2013
Posts: 18

Hi,

Thanks for the replies... But i still have a query - if the MAXMSGL is increased from 4 to 16 (so 4 times the original value) , and if there are 1000 msg/sec, will it impact on the way it is stored in memory buffer before written to disk? i mean will there be any buffer (with for Queue manager or channel) based on this attribute?

regards
cg
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fjb_saper
PostPosted: Fri Dec 08, 2017 5:10 am Post subject: Reply with quote

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With the latest versions the buffers are best handled by the qmgr and you should not change them (qm.ini) unless so directed by IBM.
For earlier versions of the product you would probably open a PMR to get some guidance. If you are experiencing performance problems you think are related to buffers, open a PMR.

Have fun
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bruce2359
PostPosted: Fri Dec 08, 2017 8:18 am Post subject: Reply with quote

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Joined: 05 Jan 2008
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Location: US: west coast, almost. Otherwise, enroute.

fjb_saper wrote:

It may take up to 2 seconds to load a big message into java memory..., a small one is loaded in a matter of milliseconds...

Given the 100MB max message size size supported in IMQ, both 4MB and 16MB seem small.

If you are going to address performance, I'd strongly suggest that before you begin fiddling with MQ internals in the .ini file, better to install more RAM.
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Andyh
PostPosted: Fri Dec 08, 2017 9:20 am Post subject: Reply with quote

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Joined: 29 Jul 2010
Posts: 150

Assuming a reasonably current service level there should be no significant performance issues in the queue manager through increasing MAXMSGL.
It is however possible that you've got applications that query the QMGR MAXMSGL and then use a buffer size on MQGET based upon that value. If that were the case (it is NOT best practice) then there would be some potential performance implication to increasing the MAXMSGL.
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