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| sbabbar98 |
 Posted: Thu Mar 17, 2005 11:26 pm Post subject: MQ Setup Question |
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Newbie
Joined: 13 Mar 2005
Posts: 9
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Hello,
We are setting up MQ Cluster in our environment here .I have couple of quick questions.
1) While creating the queue manager , Should I be using the default logging method or Linear logging method using “crtmqm -ll -q QM_NAME” .What is the recommended way ?
2) Also I would like to know What is the Best Practices for taking the MQ Series Backup in Prod environment.? would it be using rcdmqimg. If So ,Can you point me to the Link for taking the Backup and restore using rcdmqimg./ rcrmqobj commands
Thanks in advance.
SB |
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| csmith28 |
| Posted: Fri Mar 18, 2005 1:53 am Post subject: Re: MQ Setup Question |
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Grand Master
Joined: 15 Jul 2003
Posts: 1196
Location: Arizona
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| sbabbar98 wrote: |
1) While creating the queue manager , Should I be using the default logging method or Linear logging method using “crtmqm -ll -q QM_NAME” .What is the recommended way ? |
Many will argue with me but I prefer circular logging. Note: when you are creating these MQManagers you may also want to specify the Dead Letter Queue with the -u argument and unless you are happy with having 3 Primary -lp logs and 2 Secondary -ls logs for persistent messages you will want to read up on what the WMQ Systems Adminstration Guide has to say about logging.
| Quote: |
2) Also I would like to know What is the Best Practices for taking the MQ Series Backup in Prod environment.? would it be using rcdmqimg. If So ,Can you point me to the Link for taking the Backup and restore using rcdmqimg./ rcrmqobj commands. |
I believe the rcdmqimg and rcrmqobj are only usefull if you are using Linear Logging. Getting a full backup of all your MQManager data requires that the MQManager be stopped. I personally prefer using the MS03 saveqmgr Support Pack that when used will create a file that will allow you to rebuild the MQManager Objects if there is a catastrophic event that caused the MQManager to be damaged or otherwise requires the MQManager to be restored/rebuilt. Note: saveqmgr will not allow you to restore messages that were in flight at the time of the catastrophy.
My philosophy is that if something happens that is so bad that an MQManager is damaged beyond repair the loss of a handfull of messages pales in signifigance. Like I said there are those that will argue with me over this but, it works for me.
Whether you are using Linear or Circular it's a good idea to use the saveqmgr Tool.
The MS03 Support Pack can be downloaded from the IBM Site and details on the rcdmqimg and rcrmqobj commands can be found in the WMQ Systems Administration Guide.
Future posts of this nature should probably go on the MQSeries Installation/Configuration Support board.
Welcome to MQSeries.net
Regards,
Chris
_________________
Yes, I am an agent of Satan but my duties are largely ceremonial. |
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| sebastianhirt |
| Posted: Fri Mar 18, 2005 2:28 am Post subject: |
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Yatiri
Joined: 07 Jun 2004
Posts: 620
Location: Germany
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Hi,
We have got linear on most of our AIX (the important ones) and Circular on the Windows and the other AIX. I sort of agree with you Chris. Linear logging is for sure sufficient for most scenarios. (Apart from that I would recomend using SaveQMGR with both loggingtypes)
I guess it is (at least a bit) a personal preference what type of logging to use.
Also you have to see that linear loging requires additional overhead/administration to purge the obselete logs. ( AFAIK, there is a support pack that is taking care of it).
IBM is recomending to have your logfiles on a seperate file system (i.e. on a fast seperate disk) because it improves performance when it comes to Persistent messaging. That might also be something you want to consider.
So far my 2 cents.
cheers
Sebastian |
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| fjb_saper |
| Posted: Fri Mar 18, 2005 10:55 am Post subject: |
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Grand High Poobah
Joined: 18 Nov 2003
Posts: 20756
Location: LI,NY
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Chris, Sebastien,
I beg to differ a little bit.
You should determine what type of logging you need and nobody will absolve you of that responsibility. This will depend entirely on the type of messages you send.
If you send/receive important, persistent, fire and forget messages and you want guaranteed delivery I would say that linear logging is a must.
If your traffic consists only of non persistent request / reply messages with expiration, circular logging it is.
Anything in between, your bet is as good as mine.
Remember you cannot switch mid flight. You would need to delete and recreate the qmgr in linear logging.
Enjoy  |
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| PeterPotkay |
| Posted: Fri Mar 18, 2005 12:41 pm Post subject: |
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Poobah
Joined: 15 May 2001
Posts: 7722
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Just got back from an IBM MQ class, and during the break the teacher and I got into this discussion.
He said:
If an object (like a queue) becomes damaged, if you have linear logging, you can recreate the queue on the fly. If you have circular, then you have to usually stop the QM, delete the bad q file, start the QM and recreate the queue. Fortunatly damaged queues are rare.
If you have linear logging, you can restore persistent messages to the queue, but only if they were NOT gotten off of the queue and the get was committed. In other words, if a queue had 10,000 messages at 12:00, an app does 6,000 MQGETs and issue MQCMIT at 12:05, and the queue becomes useless at 12:10, you can only restore the 4,000 messages that were never gotten. The original 6,000 messages cannot be restored. MQ has relinqushed all responsibility for those 6,000 messages, because the app commited them.
For shops that use primarily non persistent messages, the only benifit to linear is the ability to recreate damaged objects on the fly.
For shops that send persistent messagesm the logs will only help for comitted persistent messasges sitting in queues, and damaged objects.
_________________
Peter Potkay
Keep Calm and MQ On |
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| Michael Dag |
| Posted: Fri Mar 18, 2005 1:31 pm Post subject: |
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Jedi Knight
Joined: 13 Jun 2002
Posts: 2607
Location: The Netherlands (Amsterdam)
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| PeterPotkay wrote: |
The original 6,000 messages cannot be restored. MQ has relinqushed all responsibility for those 6,000 messages, because the app commited them.
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because the app committed them MQ IS NO LONGER responsible for those messages. That's why only the 4,000 message are restored because MQ IS STILL responsible.
I think technically some form of forward recovery from a certain point in time takes place, but as the log is 'replayed' MQ finds out those 6,000 where gotten and should no longer be on the restored queue.
If you want to be able to replay the log information use re-Quest as the information is still there.
ps Peter... you've got a pm 
_________________
Michael
MQSystems Facebook page |
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| sebastianhirt |
| Posted: Mon Mar 21, 2005 1:37 am Post subject: |
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Yatiri
Joined: 07 Jun 2004
Posts: 620
Location: Germany
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Hi,
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| If you send/receive important, persistent, fire and forget messages and you want guaranteed delivery I would say that linear logging is a must. |
Tell me if I am wrong. But I don't think that guarantied delivery is dependant on the logging type.
IMHO Peters example is sort of making my point. If my only benefit from linear loggin is that I can recreate queues (and so on) on the fly, what is the point then in having linear logging and have to care about purge and Archive of the logs? I strongly belive that here is the point where it starts to be personal preference. Well of course you need to take into account your business needs.
Lets assume the following. You have let me say 1 Server where your Broker is running. The Broker is connected to SAP on the one end and to 500 different queue managers where the xyz application is hosted on the other end.
Now, to restart your Broker queue manager might have a huge impact. Here you definately want to have the benefit/s of linear logging.
But on that 500 other queue managers, I could imagine, to go with circular logging for farious reasons...
cheers & feel free to tell me if I am wrong...
Sebastian |
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| bower5932 |
| Posted: Mon Mar 21, 2005 5:51 am Post subject: |
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Jedi Knight
Joined: 27 Aug 2001
Posts: 3023
Location: Dallas, TX, USA
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| sebastianhirt wrote: |
| Tell me if I am wrong. But I don't think that guarantied delivery is dependant on the logging type. |
Not to split hairs, but we like to say assured delivery. And to be honest, I would think that assured delivery doesn't care what kind of logging you use. I always envisioned the logging as something you did for backup and recovery as opposed to assured delivery. |
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| PeterPotkay |
| Posted: Mon Mar 21, 2005 9:30 am Post subject: |
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Poobah
Joined: 15 May 2001
Posts: 7722
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I got think the best scenario for Linear Logging is when you have persistent messages that sit on queues. The longer they sit on the queues, the more oppourtunity there is for the QM to crash while you have persistent messages on queues that need to be restored.
Of course, you are a lot better off if the logs are kept on a separate hard drive too, to protect against the drive that houses the QM going down.
But if you have circular logging, and the the disks are mirrored, the chances of you losing your persistent messages drops significantly.
If I was designing an MQ system that was transporting messages about missle launches, or organ donations, maybe I would put up with the hassle of maintaining those linear logs, but otherwise, I just don't see that the pros of linear logging outweigh the cons. How often does a queue become damaged? (not very often).
_________________
Peter Potkay
Keep Calm and MQ On |
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| fjb_saper |
| Posted: Mon Mar 21, 2005 1:31 pm Post subject: |
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Grand High Poobah
Joined: 18 Nov 2003
Posts: 20756
Location: LI,NY
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We run a scenario where assured delivery is a must for data consistency.
Our messages are persistent and we use linear logging.
We use the java support pack for linear logging and attempt to offload the logs once a day. The log archive is kept for 10 to 20 days.
Everything is automatic and scripted. Absolutely no manual intervention!
So who's talking about hasle there ??
If your messages are not persistent and you do not run linear logging or sync point, you cannot claim assured delivery:
a) non persistent messages can get lost in channel communication
b) persistent messages can be lost to damaged objects (queues)
c) messages can be lost due to lack of transaction coordination
Syncpoint and Linear logging allow you to be steadfast in any of these worst case scenarios.
Enjoy |
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| PeterPotkay |
| Posted: Mon Mar 21, 2005 2:17 pm Post subject: |
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Poobah
Joined: 15 May 2001
Posts: 7722
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fjb_saper,
Why do you keep the logs for 10-20 days?
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a) non persistent messages can get lost in channel communication
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Not if the channel speed is set to NORMAL.
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b) persistent messages can be lost to damaged objects (queues)
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Yup. One of the best reason for Linear Logging it seems.
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c) messages can be lost due to lack of transaction coordination
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Same problem whether you have circular or linear.
_________________
Peter Potkay
Keep Calm and MQ On |
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| fjb_saper |
| Posted: Mon Mar 21, 2005 6:10 pm Post subject: |
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Grand High Poobah
Joined: 18 Nov 2003
Posts: 20756
Location: LI,NY
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Peter,
I did not say we kept the logs. I said we keep the logs archive.
This is more just because we can. No specific reason. Disaster recovery purpose wise one or two days would suffice.
Thanks
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