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| lnm |
 Posted: Fri Jan 30, 2004 9:40 am Post subject: Question: Dead Letter Q...in a different File Sys in UNIX? |
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Apprentice
Joined: 12 Mar 2002
Posts: 43
Location: Florida
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| Has anyone taken the Dead Letter Queue and put it into a different files system in UNIX? What are the plusses and minuses? What do we need to look out for if we do this? |
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| Michael Dag |
| Posted: Fri Jan 30, 2004 10:46 am Post subject: |
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Jedi Knight
Joined: 13 Jun 2002
Posts: 2607
Location: The Netherlands (Amsterdam)
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Besides the fact that I don't think it is possible to store a single queue of a QueueManager on a seperate filesystem...
Why do you want to do this??? 
Michael |
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| lnm |
| Posted: Mon Feb 02, 2004 10:23 am Post subject: |
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Apprentice
Joined: 12 Mar 2002
Posts: 43
Location: Florida
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| The concern is, if a particular queue gets full and messages start going to the dead letter queue, we don't want the file system getting filled. I'm not convinced it's a good idea and I was hoping someone else had some insight to this. |
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| Michael Dag |
| Posted: Mon Feb 02, 2004 10:30 am Post subject: |
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Jedi Knight
Joined: 13 Jun 2002
Posts: 2607
Location: The Netherlands (Amsterdam)
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Where are the messages coming from?
from another Queuemanager or application directly connected to your Queuemanager?
Michael |
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| lnm |
| Posted: Mon Feb 02, 2004 11:49 am Post subject: |
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Apprentice
Joined: 12 Mar 2002
Posts: 43
Location: Florida
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| I don't know that the answer to your question really matters....that is, it doesn't matter why the message went to the dead letter queue. The issue is for the dead letter messages not to fill up the /var/mqm filespace and prevent applications from running. Does that make sense. Our availability manager has raised this concern. |
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| bduncan |
| Posted: Wed Feb 04, 2004 5:02 pm Post subject: |
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Padawan
Joined: 11 Apr 2001
Posts: 1554
Location: Silicon Valley
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lnm,
What you are saying makes sense. However, I feel you'll stand to gain more by putting the queues and logs directories on separate partitions. I've had /var/mqm fill up on me several times, and typically it was because we allocated too many secondary circular logs, or one of our application queues filled up - as opposed to the dead letter queue getting too big.
In fact, I'd want my "applications to be prevented from running" if my dead letter queue filled up /var/mqm. The fact that so many messages are piling up on the dead letter queue is a symptom of some other problem that should be diagnosed before my applications are allowed to continue. Furthermore, you can set the MAXDEPTH and MAXMSGSIZE attributes on the dead letter queue to values which will prevent it from taking up a huge amount of disk space.
Lastly, you should consider running a dead letter handler that monitors the dead letter queue and deals with dead letter messages as they get put to queue so that they don't pile up.
_________________
Brandon Duncan
IBM Certified MQSeries Specialist
MQSeries.net forum moderator |
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| jefflowrey |
| Posted: Thu Feb 05, 2004 5:39 am Post subject: |
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Grand Poobah
Joined: 16 Oct 2002
Posts: 19981
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| bduncan wrote: |
| Furthermore, you can set the MAXDEPTH and MAXMSGSIZE attributes on the dead letter queue to values which will prevent it from taking up a huge amount of disk space. |
I don't know that I'd do that, myself. The last place I'd want to be is where messages couldn't go on the DLQ because they were too big or because the MAXDEPTH was too small. 
_________________
I am *not* the model of the modern major general. |
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| wmqiguy |
| Posted: Thu Feb 05, 2004 11:17 am Post subject: |
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Centurion
Joined: 09 Oct 2002
Posts: 145
Location: Florida
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From a purely technical standpoint, I don't see why you couldn't create a file system for:
/var/mqm/qmgrs/QMGR_NAME/queues/SYSTEM!DEAD!LETTER!QUEUE
I'm just afraid you are only dealing with the symptom instead of with the cure. Regardless of where the DLQ is located, there are ultimately finite resources.
The bigger issue (and Mr. Duncan already alluded to it) is how you are going to react when something hits the DLQ, so that you can intervene before those resources are expended? In other words, what is providing your safety net?
Are you using monitoring tools to get notified? Will you rely on a Dead Letter Handler? Custom code/scripting? Relying on separate filesystems might not be the best method of providing a safety net.
Good Luck!  |
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