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RE: SCN scheme 3

From: Ehresmann, David <David.Ehresmann_at_ps.net>
Date: Tue, 15 Apr 2003 09:48:37 -0800
Message-ID: <F001.005817FC.20030415094837@fatcity.com>


Sorry it has taken me so long to answer this. I didn't even realize that you had responded. I did a >show parameter max and I got a:

max_commit_propagtion_delay 700.

I did not change it to that. The only other timing parameter I changed was timed_statistics=true. It must be the default? thanks,
David Ehresmann.

-----Original Message-----
Sent: Monday, April 07, 2003 3:05 PM
To: Multiple recipients of list ORACLE-L

Since no-one else has answered, I'll
take a guess.

Historically OPS used to have two options for synchronising SCNs across multiple
instances, 'broadcast on commit' and 'Lamport'. The default was Lamport, but if you modified the max_commit_propagation_delay downwards from its default value of 700 (centiseconds) then at some low value (possibly about 10) the database would switch to 'broadcast on commit'.

I guess Oracle have come up with a clever new (lazy ?) way of maximising the degree of synchronisation whilst minimising the delay at any one instance, and called it 'Scheme 3'.

Have you modified the value of max_commit_propagation_delay or any other parameter which looks like a timing parameter to make this happen ? Or are you on some platform with a super-low latency for messaging ?

Regards

Jonathan Lewis
http://www.jlcomp.demon.co.uk

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> List, does anybody know what this means:
>
> SCN scheme 3
>
> It occurs it the alert log upon startup.
> thanks,
>
> David Ehresmann
>

-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: Jonathan Lewis
  INET: jonathan_at_jlcomp.demon.co.uk

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Author: Ehresmann, David
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Received on Tue Apr 15 2003 - 12:48:37 CDT

Original text of this message

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