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| Express queues written to disk. |
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| Gideon |
 Posted: Mon Jan 11, 2010 1:26 pm Post subject: Express queues written to disk. |
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Chevalier
Joined: 18 Aug 2009
Posts: 403
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I am using WMQ 7.0.1
I am sending message to queues at a high rate that were being written to disk.
I fixed a simular problem on AIX by setting the TuningParameters (specifically DefaultQBufferSize) to a large number (104857600)
I had been setting the value to 1048576, because Suppor Pack MP6N (Performance report) seemed to indicate that the max value was 1048576. However a poster on thiese boards suggested I set the value to 100mB. I did and it fixed the problem.
Now I have the same problem on WMQ 7.0.1, on Windows 2008.
I set the Registry values to 104857600 (100mb), but it does not work
Is this value smaller on WMQ 7.0.1 on WIndows server 2008 ?
Does anyone have a link for what the max of this value should be ?
Thanks |
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| Gideon |
| Posted: Mon Jan 11, 2010 1:45 pm Post subject: |
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Chevalier
Joined: 18 Aug 2009
Posts: 403
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| I just found the doc, The max is 100 MB on both Windows and AIX |
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| bruce2359 |
| Posted: Mon Jan 11, 2010 1:54 pm Post subject: |
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Poobah
Joined: 05 Jan 2008
Posts: 9469
Location: US: west coast, almost. Otherwise, enroute.
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Do a google search on DefaultQBufferSize. There are a few documents worth reading - one from Hursley.
| Quote: |
| I fixed a simular problem ... |
What problem? Are/were you missing SLAs?
_________________
I like deadlines. I like to wave as they pass by.
ב''ה
Lex Orandi, Lex Credendi, Lex Vivendi. As we Worship, So we Believe, So we Live. |
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| Gideon |
| Posted: Mon Jan 11, 2010 1:57 pm Post subject: |
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Chevalier
Joined: 18 Aug 2009
Posts: 403
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With the memory buffer set to 100 MB, I still see a small quick blip of disk activity when writing express (non-persistent ) message to an express queue.
But it does not look like a disk spill over or lack of memory
I send meeages to WMQ for about 60 seconds
There is no Disk activity for the first 30 seconds.
Then for about a second I get a slight burst of activity on the disk.. The 'q' file is being written to.
The after a second, the disk activity goes away.
It returns again about 50 seconds into the run, but dissappears immeidately again.
I am pretty sure this is not a memory alloc problem. I set the memory tuning parameter to max, and if I do not do that , when th disk activity starts, it does not stop, it keeps persistenting the express message to disk
Does anyone know what is going on.
Is WMQ periodically writing statistics to the q file header, etc ?
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| bruce2359 |
| Posted: Mon Jan 11, 2010 2:30 pm Post subject: |
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Poobah
Joined: 05 Jan 2008
Posts: 9469
Location: US: west coast, almost. Otherwise, enroute.
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Again, what is the problem?
You have described an affect of WMQ (not a problem), namely: mq writes buffer contents to disk when buffers are near full.)
Are you expecting no disk i/o? occasional i/o? frequent i/o?
Are your apps creating persistent messages? or non-persistent messages?
Is the consuming program alive and well, and consuming the messages? Are there other apps creating messages at the same time?
_________________
I like deadlines. I like to wave as they pass by.
ב''ה
Lex Orandi, Lex Credendi, Lex Vivendi. As we Worship, So we Believe, So we Live. |
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| Gideon |
| Posted: Mon Jan 11, 2010 2:48 pm Post subject: |
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Chevalier
Joined: 18 Aug 2009
Posts: 403
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You are correct. There is no severe problem here. The consumers are working properly, so is the app
What I am trying to determine is what is exactly happening, because I will be eventually asked why there is disk activity here.
In short, the Memory parameter is set extremely high, so I do not think the memory is even close to full.
No matter what valuue I set DefaultQBufferSize to, it will show a very very short disk activity about 30 seconds into the run.
What I am trying to figure out is what MQ is actually doing there.
What ever MQ is writing, it is not the contents of the memory, or I would see a lot more disk IO for a longer period of time.
It looks like it is writing some sort of snapshort of the buffer size to the q header in case there is a qmgr restart (Ijust my best guess).
Does anyone know what is going on here ? |
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| Vitor |
| Posted: Mon Jan 11, 2010 2:57 pm Post subject: |
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Grand High Poobah
Joined: 11 Nov 2005
Posts: 26093
Location: Texas, USA
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| Gideon wrote: |
| Does anyone know what is going on here ? |
If anyone knows for sure, they work at Hursley. You can wait for a response here (if one arrives), or raise a PMR.
I leave the decision to your good judgement.
_________________
Honesty is the best policy.
Insanity is the best defence. |
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| mvic |
| Posted: Mon Jan 11, 2010 3:03 pm Post subject: |
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Jedi
Joined: 09 Mar 2004
Posts: 2080
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| Gideon wrote: |
| No matter what valuue I set DefaultQBufferSize to, it will show a very very short disk activity about 30 seconds into the run. |
How much data? How long does it take?
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| What I am trying to figure out is what MQ is actually doing there. |
A queue manager is a complex system, it is not only serving one queue. Do you know for sure which files is/are being touched?
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| What ever MQ is writing, it is not the contents of the memory, or I would see a lot more disk IO for a longer period of time. |
Are you referring to the 100 Mb buffer? It does not seem a likely design that if a buffer fills then the whole thing is written to disk. It seems more likely that only the surplus will spill to disk. Anyway this is pure speculation about what is going on. It could be something altogether different.
Have you tried turning on MQ statistics gathering for all queues on the qmgr, and analysing the results? There are tools/products you can buy that will help analyse these, or alternatively perhaps look at the statistics sections of the Montoring MQ manual and collect raw numbers and analyse them directly. |
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| bruce2359 |
| Posted: Mon Jan 11, 2010 3:41 pm Post subject: |
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Poobah
Joined: 05 Jan 2008
Posts: 9469
Location: US: west coast, almost. Otherwise, enroute.
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| Quote: |
| What I am trying to figure out is what MQ is actually doing there. |
It is managing your messages, and ensuring that they are written (hardened) to disk to ensure that they are not lost.
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| What ever MQ is writing, it is not the contents of the memory, or I would see a lot more disk IO for a longer period of time. |
I'd be surprised if IBM offers you one of those "here's exactly how that works..." answers. Why do you believe that there would be more disk i/o for a longer period of time?
_________________
I like deadlines. I like to wave as they pass by.
ב''ה
Lex Orandi, Lex Credendi, Lex Vivendi. As we Worship, So we Believe, So we Live. |
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