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| tborrome |
 Posted: Mon Apr 22, 2002 1:11 pm Post subject: |
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Novice
Joined: 03 Apr 2002
Posts: 17
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I'm using persistent messages for my JMS application. I see that the messages are getting persisted in the file: C:MQSeriesqmgrsQM_tyrone_ntQUEUES@MANGLED\0E000000Q
Some questions:
1) Is there a way to change this default location?
2) Does anyone know how MQseries persist messages? Does it do synchronous IO or async?
Thanks,
Tyrone
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| StefanSievert |
| Posted: Mon Apr 22, 2002 3:23 pm Post subject: |
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Partisan
Joined: 28 Oct 2001
Posts: 333
Location: San Francisco
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| Quote: |
On 2002-04-22 14:11, tborrome wrote:
1) Is there a way to change this default location?
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I am assuming Windows as your platform and the answer in that case is yes. When you've installed the product, it asked you for a program file and a data directory. The data directory is the one where the object definitions get created. You can probably change the location after the fact by bringing down the queue manager, copying some directories and doing some 'dirty' registry updates, but the usual disclaimer applies to that procedure... 
| Quote: |
2) Does anyone know how MQseries persist messages? Does it do synchronous IO or async?
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My statement to this question would be: Persitent messages are synchronously hardened to the log file, NOT necessarily the Q file you mentioned during MQPUT processing; i.e. when you get a MQCC_OK, the message has been persisted to the log. It won't work any other way, I guess. Now, when the message will be written to the Q file is most likely an asynchronous process run by the MQSeries code based on log usage and other (performance related?) considerations that shouldn't be of any concern from an application programming perspective. Where does you interest in this come from, has any 'strange' behavior occurred in your environment?
Hopefully somebody will jump in if I talk complete nonsense here.
Cheers,
Stefan
_________________
Stefan Sievert
IBM Certified * MQSeries
In the end everything is right. If not, it's not the end.
[ This Message was edited by: StefanSievert on 2002-04-22 16:24 ] |
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| tborrome |
| Posted: Tue Apr 23, 2002 6:09 am Post subject: |
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Novice
Joined: 03 Apr 2002
Posts: 17
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Stefan,
Thanks for your replies. I'm asking about the persistent mechanism because I'm concerned about the quality of service - how does MQseries assure that the persisted messages can survive a crash. My application needs to make sure that all persisted messages get recovered in case the system crashes. If it does synchronous IO, I believe that this is safe but if it's asynchronous, there may be some messages that do not get recovered. Do you know where this is documented?
thanks and regards,
Tyrone
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