Fwd: Re: SCN scheme 3 -- clarification on

I had logged a TAR with Oracle Support on why the alert.log showed that the Database Instance was using Lamport inspite of having set max_commit_propagation_delay to 0.

The clarification I received from the Support Analyst was :

"
This is expected that it gives a message of using "Lamport SCN generation" scheme, it uses SCN server implementation.

   This is documented in the Note: 226561.1 which is a internal note and mentions the below line.

   --------------From Note:226561.1---------------    On Tru64, "Picked Lamport Server scheme to generate SCNs" is reported for MCPD < 700; this is actually a misnomer

   since it is not a Lamport implementation,and Broadcast-On-Commit is used.

   This means that Broadcast-On-Commit is used. "

Hemant

>Date: Tue, 08 Apr 2003 21:46:25 +0800
>To: ORACLE-L_at_fatcity.com
>From: Hemant K Chitale <hkchital_at_singnet.com.sg>
>Subject: Re: SCN scheme 3
>
>
>On my 9iRAC 9.2.0.2 Database I set max_commit_propagation_delay to 0,
>yet the alert.log indicates that the Instance is starting with Lamport Server
>SCN generation. I wonder why.
>Hemant
>At 12:04 PM 07-04-03 -0800, you wrote:
>
>>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
>>
>> The educated person is not the person
>> who can answer the questions, but the
>> person who can question the answers -- T. Schick Jr
>>
>>
>>One-day tutorials:
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>>The Co-operative Oracle Users' FAQ
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>>
>>
>>----- Original Message -----
>>To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com>
>>Sent: 28 March 2003 21:18
>>
>>
>> > 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
>>
>>Fat City Network Services -- 858-538-5051 http://www.fatcity.com
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>
>Hemant K Chitale
>My personal web site is : http://hkchital.tripod.com

Hemant K Chitale
My personal web site is : http://hkchital.tripod.com

-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: Hemant K Chitale
  INET: hkchital_at_singnet.com.sg

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