Juan
In the Dec 2001 edition of the Student Guide, that statement appears on
page 14-12. I think the paragraph preceding the one you quoted sets the
context for the statement a bit:
How to Solve B-Tree Index Performance Degradation
The more levels an index has, the less efficient it may be. Additionally, an
index with many rows deleted might not be efficient. Typically, if 15% of
the index data is deleted, then you should consider rebuilding the index.
You should rebuild your indexes regularly. However, this can be a
time-consuming task, especially if the base table is very large . . . the
paragraph then goes on to describe the index rebuilding options.
Juan - If you search the archive for this list, you will find where the
topic of rebuilding indexes has been discussed many times. This should give
you some more background on the issue. Second, while the Student Guides are
great for helping pass the OCP, they are primarily oriented toward people
new to Oracle. As you become more experienced in Oracle, you should dig
deeper, particularly on vague topics like "when to rebuild indexes". Third,
while the sentence in the Student Guide does say "rebuild your indexes
regularly", the context of the statement is really discussing all the
wonderful new Oracle9i features that make rebuilding indexes a less onerous
task.
Dennis Williams
DBA, OCP
Lifetouch, Inc.
dwilliams_at_lifetouch.com
-----Original Message-----
From: Juan Miranda [mailto:j.miranda_at_sermatica.es]
Sent: Tuesday, February 17, 2004 7:24 AM
To: oracle-l_at_freelists.org
Subject: RE: Rebuild Indexes
Oracle 9i Performance Tuning
Student Guide Vol1.
D11299GC10
July 2001
12- Application tuning
12-11 bitmap indexes.
Juan Miranda
Oracle Certified Professional.
-----Mensaje original-----
De: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] En
nombre de Niall Litchfield
Enviado el: martes, 17 de febrero de 2004 13:20
Para: oracle-l_at_freelists.org
Asunto: RE: Rebuild Indexes
Hi Juan
I couldn't actually find your quote in the Performance Tuning Guide for 8.1=
.7, 9.2 or 10.1. Is it perhaps some other book?=20
Niall Litchfield
Oracle DBA
Audit Commission
+44 117 975 7805=20
> -----Original Message-----
> From: j.miranda_at_sermatica.es=20
> Sent: 17 February 2004 10:41
> To: j.miranda_at_sermatica.es; oracle-l_at_freelists.org
> Subject: RE: Rebuild Indexes
>=20
>=20
>=20
> Hi
>=20
> May script do just original post (vidya kalyanaraman) as for.
> No more.=20
>=20
> May be is not adecuate for your system.=20
> Anyway you can stop it when you want: a simple CTRL+C.
>=20
> In my mail I say:=20
> "Take care in production because VALIDATE STRUCTURE do some=20
> tipe of lock."
>=20
> I have a very busy database and I execute this script very=20
> care and control.
> I do it once a year and this reduced to 1/3 the space ocupied=20
> by indexes.
>=20
> I will no discuss if it is good or not to rebuild indexes but...
> Oracle Performance Tuning Manual 12-12:
> "You sould rebuild your indexes regularly. However, this can be a
> time-consuming task, especially if the base table es very large."
>=20
> Sorry if it caused problems in your system but ask Oracle for a better
> rebuild method, not me.
>=20
> I forgot to add an "alter session set SORT_AREA_SIZE=3D25000000;". This=
> do it faster.
>=20
> Grettings.
>=20
>=20
> -----Mensaje original-----
> De: oracle-l-bounce_at_freelists.org=20
> [mailto:oracle-l-bounce_at_freelists.org] En
> nombre de Richard Foote
> Enviado el: viernes, 13 de febrero de 2004 14:59
> Para: oracle-l_at_freelists.org
> Asunto: Re: Rebuild Indexes
>=20
> When to rebuild indexes, hummm, this is all rather new and exciting ;)
>=20
> Juan, I notice with interest that your script:
>=20
> - performs an analyze validate structure on all indexes
> - rebuilds all indexes if guilty of having more than 2 levels
> - rebuilds all indexes with more than 10% deleted rows
>=20
> Running such a script on our production databases at my=20
> current site would:
>=20
> - cripple performance for up to approximately 14 hours=20
> (depending on
> database) performing just the analyze step
> - rebuild every single one of our larger, 3+ level=20
> indexes (don't want
> to think about the cost of this)
>=20
> for practically *no* benefit.
>=20
> The 3+ criteria does "accidentally" rebuild the handful we've=20
> identified as
> being candidates for an occasional rebuild but boy, what an=20
> incredible price
> to pay !!
>=20
> I think not ...
>=20
> Richard Foote
>=20
> ----- Original Message -----
> From: "Juan Miranda" <j.miranda_at_sermatica.es>
> To: <oracle-l_at_freelists.org>
> Sent: Friday, February 13, 2004 7:14 PM
> Subject: RE: Rebuild Indexes
>=20
>=20
>=20
> Hi
>=20
> Try this.
> This do not use a cursor so you can stop it when you what.
> Take care in production because VALIDATE STRUCTURE do some=20
> tipe of lock.
>=20
>=20
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> +++++++++++=3D
> +++
> -- Juan Miranda Serm=3DE1tica 06/AGO/2002
> -- Utiliza VALIDATE STRUCTURE -> OJO en producci=3DF3n. Puede generar =3D
> errores
> ORA-00054.
> -- OJO nolog -> NO usar con stand by
>=20
>=20
> set serveroutput on size 1000000
> set pagesize 0
> set feedback off
> set echo off
> set trimspool on
>=20
> spool c:\reb_index1.sql
>=20
> DECLARE
> dbname varchar2(20);
> wday varchar2(11);
> BEGIN
> dbms_output.put_line('set echo off');
> dbms_output.put_line('set feedback off');
> dbms_output.put_line('set head off');
>=20
> dbms_output.put_line('spool c:\reb_index2.sql');
> dbms_output.put_line('prompt set feedback on');
> dbms_output.put_line('prompt set echo on');
> dbms_output.put_line('prompt spool c:\reb_index2.log');
>=20
> FOR t IN (select owner, index_name from dba_indexes where=20
> owner not =3D
> in
> ('SYS','SYSTEM') order by owner,index_name) LOOP
>=20
> dbms_output.put_line('prompt --Analizando
> '||t.owner||'.'||t.index_name);
>=20
> dbms_output.put_line('Analyze index=20
> '||t.owner||'.'||t.index_name||'
> validate structure;');
>=20
> dbms_output.put_line('select ' || '''' || 'Alter index '=20
> || t.owner =3D
> ||
> '.' || t.index_name || ' rebuild online;' || ''''|| ' from=20
> index_stats =3D
> where
> (height > 2) or
> (10<=3D3Ddecode(lf_rows_len,0,NULL,((del_lf_rows_len/lf_rows_len
> )*100)));')=3D
> ;
>=20
> END LOOP;
>=20
> dbms_output.put_line('prompt spool off');
> dbms_output.put_line('spool off');
> dbms_output.put_line('@c:\reb_index2.sql');
>=20
> END;
> /
> spool off
>=20
> @c:\reb_index1.sql
>=20
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> +++++++++++=3D
> +++
>=20
>=20
>=20
>=20
> -----Mensaje original-----
> De: oracle-l-bounce_at_freelists.org=20
> [mailto:oracle-l-bounce_at_freelists.org] =3D
> En
> nombre de vidya kalyanaraman
> Enviado el: viernes, 13 de febrero de 2004 9:46
> Para: oracle-l_at_freelists.org
> Asunto: Rebuild Indexes=3D20
>=20
> Hi
> It may be a silly thing to ask, but I am stuck right now.=3D20
> I have been given a task to find out the indexes which need to be=3D20
> rebuilt. There are around 3000 Indexes. I know I can run=20
> the following =3D
>=20
> command
> "analyze index <Index> VALIDATE STRUCTURE " =3D20
>=20
> for a single index and then find the rows from index_state=20
> based on=3D20
> del_lf_rows_len/lf_rows_len > 20%. =3D20
> Does anyone have a script for dynamically finding out the=20
> indexes that=3D20
> are the candidates for rebuilding? How do you normally handle=3D20
> situations like this?
>=20
> TIA
> Vidya
>=20
>=20
>=20
>=20
>=20
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>=20
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>=20
>=20
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Received on Tue Feb 17 2004 - 08:54:37 CST
