Re: Difference - Rebuild and Analyze index

What version of database and OS? I never found this behaviour? on 7.3.4.5 on HP 11...

Regards
Rafiq

Reply-To: ORACLE-L_at_fatcity.com
To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com> Date: Wed, 16 Oct 2002 09:43:51 -0800

At least on my DB's doing ALTER INDEX <index_name> REBUILD does in fact populate the statistics.
I discovered this by accident on one RBO DB which started giving poor performnce after doing some
REBUILDs (OPTOMIZER_MODE=CHOOSE).

                       ora ak
                       <ora_magic_at_yahoo.        To:       Multiple 
recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
                       com>                     cc:
                       Sent by:                 Subject:  Re: Difference - 
Rebuild and Analyze index
                       root_at_fatcity.com


                       10/16/2002 08:49
                       AM
                       Please respond to
                       ORACLE-L

Yes Marul , I think there is a big differenece in them . When you are rebulding the index means you are re-organzing the entries in the index , may be removing the entries for the rows deleted in past and so forth so on. But this doesn't generate any statistics about index.

When you analyze index, you generate information ( statistics) about the data in index , like leaf blocks or depth of index etc.

None of these should require orther , but they have some effect .

Like if you rebuild index , after that you dont have latest statistics and queries may not perform upto mark .

-oramagic

  Marul Mehta <marul_at_zycus.com> wrote:
  Hi,

  Can anybody please tell me the difference between -

  SQL > execute DBMS_UTILITY.ANALYZE_SCHEMA('BLAH','COMPUTE',NULL,30,'FOR   ALL INDEXES');
  and
  SQL > select 'ALTER INDEX ' || INDEX_NAME || ' REBUILD ONLINE;' from   USER_INDEXES
  If I execute any one the above do i need to execute the other also?

  After how many days/hour it should be executed.

  TIA,
  Marul.

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