RE: LGWR's Writing Habits

Releasing the source code is grounds for immediate dismissal from Oracle and might in fact be grounds for legal action....

I don't think anyone wants to take that risk, and I certainly don't want to be the cause of such actions by asking someone to do it.

And Gaja didn't say he had access to the code, he said he had a friend who had access, so yes, he had to speculate before checking with his friend.

>From: "Khedr, Waleed" <Waleed.Khedr_at_FMR.COM>
>Reply-To: ORACLE-L_at_fatcity.com
>To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
>Subject: RE: LGWR's Writing Habits
>Date: Wed, 13 Dec 2000 12:56:18 -0800
>
>
>I do not understand if you have access to the source code then why do you
>have to speculate about LGWR behavior?
>
>Also it could be a good idea to ask your friend in Oracle to post some of
>the source code here in this list so that we can answer many of the
>questions we have.
>
>
>-----Original Message-----
>Sent: Wednesday, December 13, 2000 12:45 PM
>To: Multiple recipients of list ORACLE-L
>
>
>Hello everyone,
>
>A couple of days ago I had posted a response to someone's query
>about copy latches and in that discussion I had mentioned that
>the 1/3 full event of the redo log buffer will really not 'kick
>in' unless log_buffer is set to at least 1Mb. I must confess
>that the number here is actually 3Mb and not 1Mb as posted
>before. I apologize for that typo.
>
>However, the fact remains that from Oracle8, LGWR will not be
>posted by the 1/3rd full event of the redo log buffer, unless
>there are at least 1 Mb worth of redo entries in the log_buffer.
>In my previous posting, I said that for this to occur the
>log_buffer should be sized at least 1 Mb, but that number is
>actually even higher - 3 Mb.
>
>And the rationale behind that stems from the events on which
>LGWR writes to disk. They are as follows:
>
>1) Every 3 secs (independent of DBWR, yes this has been proven
>to be true by testing and looking up the source code).
>2) On a Commit.
>3) When DBWR posts LGWR to write. (This is to make sure that the
>redo entires are written before 'dirty' blocks are written to
>disk).
>4) On checkpoints.
>5) When the log_buffer is 1/3rd full, but subject to the
>following formula MAX(1 Mb., log_buffer/3), i.e., at least 1 Mb
>of redo entries need to be there, for the 1/3 event to occur.
>
>Now let's think about this for a minute. Realistically the need
>for the 1/3rd full event is not that critical, as events 1-4
>will take care of getting the redo entries down to disk. And
>this in no way will cause more 'log buffer space' waits than
>what the system is already experiencing.
>
>To make doubly sure that I was not 'under the influence', I
>called a very good friend of mine at Oracle, and had him check
>the source code for 8.0.5, and he corroborated my claim. We are
>doing some further digging, to determine whether 'all' or 'one'
>of the redo copy latches are used to protect the buffer, while
>'flushing' the entire contents of the log_buffer. There are 2
>references to this (one mentioning 1 copy latch and the other
>mentioning all copy latches) and we will get to the bottom of
>that and I will then post our findings.
>
>End of technical stuff;
>
>********************************************************
>Begin non-technical stuff;
>
>When I originally posted that the 1/3rd full event has changed
>in functionality in Oracle8, it was termed as a 'ludicrous
>suggestion'. Now, that comment may have gone 'just a bit too
>far' to my personal comfort, as it was directed against me
>'point blank'. I just could not hit the 'delete key' on that
>one.
>
>In light of all the 'country of origin' and 'ethnic background'
>stuff that has gone through our list in the past couple of days,
>I humbly urge all of us to exercise some caution in our
>communications. This is an forum where we cannot guage the
>poster's feelings, hence we need to make sure that we are
>sensitive to the reader's feelings.
>
>While it is absolutely OK to question the contents of a posting,
>please do it in a manner that is 'amicable'. After all, we are
>human beings first, aside of our ethnic, cultural, religious and
>political backgrounds. Let's try to respect thatm core fact.
>
>When I met Jared approx. 3 years ago at an IOUG-A conference, we
>talked about creating an Oracle listserv to 'share relevant and
>accurate information'. I don't think Jared or any one of us,
>would want this to become 'electronic battleground' for food
>fights or to be a forum to 'force and assert one's technical or
>personal ego'.
>
>This list today has a few thousand individuals from all corners
>of the world, and all of us contribute to the best of our
>abilities. Let's continue the great technical content exchange
>that we have had and let's do that with 'respect for the
>reader'. Thanks for your patience, tolerance and technical
>prowess.
>
>End non-technical stuff;
>
>********************************************************
>
>Seasons Greetings,
>
>Gaja
>
>
>=====
>Gaja Krishna Vaidyanatha
>Director, Storage Management Products, Quest Software Inc.
>Office : (972)-304-1170, E-mail : gaja_at_quest.com
>
>Author:Oracle Performance Tuning 101 by Osborne McGraw-Hill
>"Opinions and views expressed are my own and not of Quest"
>
>__________________________________________________
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>Author: Gaja Krishna Vaidyanatha
> INET: gajav_at_yahoo.com
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>Author: Khedr, Waleed
> INET: Waleed.Khedr_at_FMR.COM
>
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