You gotta imagine the British accent with it Jared. It's what you need to
take into account when a database is accessible over the Internet (otherwise
known as the "Hacking Factor") ;)
Pete
"Controlling developers is like herding cats."
Kevin Loney, Oracle DBA Handbook
"Oh no, it's not. It's much harder than that!"
Bruce Pihlamae, long-term Oracle DBA
-----Original Message-----
[EMAIL PROTECTED]
Sent: Monday, March 24, 2003 3:34 PM
To: Multiple recipients of list ORACLE-L
Jonathan,
What is the 'Haken' factor?
Jared
"Jonathan Lewis" <[EMAIL PROTECTED]>
Sent by: [EMAIL PROTECTED]
03/24/2003 02:24 PM
Please respond to ORACLE-L
To: Multiple recipients of list ORACLE-L <[EMAIL PROTECTED]>
cc:
Subject: Re: Reorganizing tables
This may have been mentioned already, but a
table re-org can be a positive threat to performance.
If your primary tables have (for example) a three-stage
life:
initial row size is small
row grows after a couple of weeks
row reaches full size after another 4 weeks,
then what value are you going to use for your
PCTFREE when you rebuild ?
If you set it to zero to avoid wasting space
for the vast percentage of rows that are full
size then many incomplete rows will end up
migrating.
If you set it to match the growth requirement
of the newest rows, then you leave lots of
empty space in the blocks that hold only old
rows.
(The optimum storage answer is to set the
Hakan factor before moving the table - but
that's not a trivial exercise because of a bug
whose number I can't remember).
Regards
Jonathan Lewis
http://www.jlcomp.demon.co.uk
For one-day tutorials:
(see http://www.jlcomp.demon.co.uk/tutorial.html )
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Next dates for the 3-day seminar:
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The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/faq/ind_faq.html
----- Original Message -----
To: "Multiple recipients of list ORACLE-L" <[EMAIL PROTECTED]>
Sent: 24 March 2003 20:53
> Thanks Jared, Rachel, Tom, Dick, Prakash, Ron
>
> Excellent points. Very much appreciated. Unfortunately at this point
people
> are asking "but have you tested it?". So I need to construct some
type of
> test that will demonstrate how much effect a reorg will have. After
I've
> answered that question, then I can move on to some of the other
issues that
> you mention. I have joked that if the results are strongly positive,
they
> won't see me much after that because I'll be touring the world
selling my
> performance solution that never occurred to anyone else.
> Our test system is cloned from an RMAN backup of production so
the tables
> should be close to production. I'm thinking of creating a new table
and
> copying the contents of a production table into it and then tracing
> full-table scans and comparing the results.
>
> Jared - is there a way to estimate block-level fragmentation?
Comparing the
> average row length with the number of blocks used?
>
> Dennis Williams
> DBA, 40%OCP, 100% DBA
> Lifetouch, Inc.
> [EMAIL PROTECTED]
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