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| yiftah_o |
 Posted: Wed Jul 24, 2002 6:32 am Post subject: qm.ini Log stanza |
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Newbie
Joined: 30 Jun 2002
Posts: 9
Location: Raanana, Israel
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Hi
in the qm.ini file there is a parameter:
LogWriteIntegrity=TripleWrite
I would like to understand what does this parameter control and what are the available options for it (beside TripleWrite).
thanks
Yiftah[/code][/quote] |
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| bower5932 |
| Posted: Wed Jul 24, 2002 8:20 am Post subject: |
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Jedi Knight
Joined: 27 Aug 2001
Posts: 3023
Location: Dallas, TX, USA
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There is some information in the System Admin manual on this:
LogWriteIntegrity=SingleWrite|DoubleWrite|TripleWrite
The LogWrite attribute specifies the method the logger uses to reliably write log records.
SingleWrite Where a non-volatile write cache is used (for example, ssa write cache enabled) then it is safe for the logger to write log records in a single write.
DoubleWrite In some cases an additional write is necessary to write log records with more integrity.
TripleWrite In some cases another additional write is necessary to write log records with complete integrity, but at the cost of performance. This is the default value. |
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| yiftah_o |
| Posted: Wed Jul 24, 2002 8:32 am Post subject: |
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Newbie
Joined: 30 Jun 2002
Posts: 9
Location: Raanana, Israel
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how can I determine the level of integrity suitable for me?
in what cases can persistent information be lost when using LogWriteIntegrity=SingleWrite ? |
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| RogerLacroix |
| Posted: Wed Jul 24, 2002 7:53 pm Post subject: |
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Jedi Knight
Joined: 15 May 2001
Posts: 3264
Location: London, ON Canada
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It goes something like this:
If you have a queue manger failure and when you tell your manager:
(1) s/he says "Who cares" then use single write.
(2) s/he paces in and out of your office while you recover the queue manager's data then use double write.
(3) s/he has security in your office with packing boxes then use triple write.
Hope that helps. 
later
Roger... |
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| yiftah_o |
| Posted: Thu Jul 25, 2002 1:17 am Post subject: |
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Newbie
Joined: 30 Jun 2002
Posts: 9
Location: Raanana, Israel
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what if my manager has security in my office with packing boxes in case performance goes down?
will it help to decrease the LogWriteIntegrity or should I pack my bags ? |
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| mrlinux |
| Posted: Thu Jul 25, 2002 5:09 am Post subject: |
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Grand Master
Joined: 14 Feb 2002
Posts: 1261
Location: Detroit,MI USA
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Well to determine the level of integrity you need,
1) How often do your systems lose power and go down ?? if more than once a year and the possible loss of messages is not easily recoverable then go for triple.
2) How often does the box crash for software reasons ??? see above
3) How hard is it to determine/recreate the data lost when the system
comes down. If you have some kind of resend process then you
can reduce the logwrites to single.
This is only my opinion !!!!!
_________________
Jeff
IBM Certified Developer MQSeries
IBM Certified Specialist MQSeries
IBM Certified Solutions Expert MQSeries |
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| yiftah_o |
| Posted: Thu Jul 25, 2002 5:16 am Post subject: |
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Newbie
Joined: 30 Jun 2002
Posts: 9
Location: Raanana, Israel
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thanks a lot guys
Yiftah |
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| Michael Dag |
| Posted: Mon Feb 16, 2004 10:14 am Post subject: |
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Jedi Knight
Joined: 13 Jun 2002
Posts: 2607
Location: The Netherlands (Amsterdam)
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Just dug up this interesting post as I am playing around with
Single/Double/Triple write logging to see the difference in persistent performance. (and there IS!  )
from a 'safety' point of view (in relation to to Single/Double/Triple write) is there difference between LINEAR and CIRCULAR logging?
i.e. if using LINEAR logging SingleWrite is 'as safe as the bank'
i.e. if using CIRCULAR logging SingleWrite is NOT 'as safe as the bank'
as CIRCULAR logs need verification if the data is really delivered, before the logspace can be released/overwritten
(which does not occur when using LINEAR logging), hence the need for TripleWrite.
Michael |
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