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| QSG - Do I have to explicitly backup the Admin structure? |
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| dogbert64 |
 Posted: Thu May 28, 2009 6:14 am Post subject: QSG - Do I have to explicitly backup the Admin structure? |
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Acolyte
Joined: 11 Jun 2003
Posts: 58
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IBM indicates that you will need to backup your QSG Application Pools often with the BACKUP CFSTRUCT command to flush out all persistent messages to the Logs for DR purposes.
We only have one pool now, with the name of QSGPOOL1 (original, ain't it?).
So I need to have BACKUP CFSTRUCT (QSGPOOL1) executed often.
My question is do I have to explicitly backup the QSG Admin structure as well with BACKUP CFSTRUCT (<admin structure>), or does MQ back it up when the Application Pool is backed up?
A second question, if our corporate Recovery Point Objective is 5 minutes (maximum amount of permissible data loss in a DR event) then wouldn't I need to ensure that this command is executed every "less than 5" minutes? |
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| bob_buxton |
| Posted: Thu May 28, 2009 11:18 am Post subject: |
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Master
Joined: 23 Aug 2001
Posts: 266
Location: England
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When a persistent message is put or got it is written to the log immediately and the log buffers are flushed out to disk when the unit of work is committed. So if you should need to recover a coupling facility there is no loss of data, all messages up to the point of failure can be recovered.
The reason for recommending frequent backups is to reduce the time to recover from the failure. When performing recovery the system has to read the backup and the logs from each of the queue managers between time of backup and time of failures - if there is no backup it will read all logs since the structure was defined which could take a very long time.
So the important question is not how much data loss you are prepared to tolerate but what is your corporate requirement for speed of recovery - how soon after a failure must your system be usable again with zero data loss?
If you have 6 queue managers and a five minute backup interval when you need to recover you will have up to 33 minutes worth of log data that needs to be read (log reading goes slightly beyond the backup start time). If all of your queue managers are heavily loaded and constrained by how fast they can write to the log it may take as long to read all of the logs but on a less constrained system it should take lot less time to read the data than that.
As for the Admin structure it only contains copies of information that is already present on the log so there is no need for it to be explicitly backed up
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Bob Buxton
Ex-Websphere MQ Development |
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| bruce2359 |
| Posted: Thu May 28, 2009 12:50 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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Phil, is that you?
A consideration is long-lived vs. short-lived messages. If all messages put to the shared-queue are immediately consumed, there will be low risk of msg loss.
Shared-queues holding long-lived messages would seem to require more frequent backup to reduce the time needed to replay the logs.
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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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| dogbert64 |
| Posted: Fri May 29, 2009 12:23 pm Post subject: |
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Acolyte
Joined: 11 Jun 2003
Posts: 58
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| Sshhhh, you're going to blow my cover. |
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| dogbert64 |
| Posted: Fri May 29, 2009 12:25 pm Post subject: |
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Acolyte
Joined: 11 Jun 2003
Posts: 58
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Thanks Bob and Bruce - you've given me good information. Looking closer at the IBM Manuals, they said what Bob did, just not quite as clear.
I've only got QSG working in our lowest of 4 environments, but I've been quite impressed with the technology so far. It does just what IBM says it will do, with no fuss so far. |
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