Re: re Rebuilding Indexes in Oracle Apps -- was RE: RE:

The article states that leaf blocks are not reused, which is indeed incorrect,
and has been for a very long time.

Hemant K Chitale <hkchital_at_singnet.com.sg> Sent by: ml-errors_at_fatcity.com
 10/17/2003 11:42 AM
 Please respond to ORACLE-L  

        To:     Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
        cc: 
        Subject:        Re: re Rebuilding Indexes in Oracle Apps -- was RE: RE:

I wonder if "it is not necessary to rebuild indexes" is also a myth.

It IS in some cases necessary
1. Indexes on monotonically increasing values [eg Conrurrent_Request_ID based on a Sequence
or even on date columns which signify when the record is created] if the table is also
purged by the same columns frequently
2. Because the disk space used by an Index can be inordinately larged after a couple of years
and index fast_full_scans are impacted

Have you administered an Oracle Applications database ? hemant

At 03:29 AM 17-10-03 -0800, you wrote:
>Hi Hemant,
>
>One word perfectly describes the Metalink article you highlighted:
>
>Crap ;)
>
>A nice example of how Oracle Corp is the greatest myth generator of them
>all !! It's all rather sad and embarressing isn't.
>
>Thanks for the headsup. Anyone in a position to get the note removed ?
>
>Cheers
>
>Richard
>
> >Quoting Metalink Note 182699.1 bde_rebuild.sql Validates and Rebuilds
>Fragmentated Indexes (8.0->9.0)
> >
> >Index fragmentation occurs when a key value changes, and the index row
is
> >deleted from one place (Leaf Block) and inserted into another.
> >
> > Deleted Leaf Rows are not reused. Therefore indexes whose columns are
> >subject to value change must be rebuilt periodically since they become
>naturally fragmentated.
> >
> >An index is considered to be 'fragmentated' when more than 20% of its
Leaf
>Rows space is
> >empty because of the implicit deletes caused by indexed columns value
>changes.
> >
> >Fragmentated indexes degrade the performance of index range scan
>operations.
>
>
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Hemant K Chitale
Oracle 9i Database Administrator Certified Professional My personal web site is : http://hkchital.tripod.com

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