Oracle-L: Re: re Rebuilding Indexes in Oracle Apps -- an update

From: <Jared.Still_at_radisys.com>
Date: Tue, 04 Nov 2003 12:29:33 -0800
Message-ID: <F001.005D591E.20031104122933@fatcity.com>

Now that I think about it, you're probably right.

I'll test it anyway, I like to see numbers. :)

Jared

"Tanel Poder" <tanel.poder.003_at_mail.ee>
Sent by: ml-errors_at_fatcity.com
11/04/2003 10:04 AM
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        To:     Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
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        Subject:        Re: re Rebuilding Indexes in Oracle Apps -- an update

Jared,

I don't see how index skip scans could benefit more from a rebuild than from coalesce (providing the index height remains the same). Skip scan doesn't scan the whole index like FFS does, it just does several scans for each value set in beginning of concatenated index (+some more mechanisms).

Maybe I'm missing something here, what did you have in mind?

Tanel.

If the index is based simply on the unique key, and for some reason you are
using index_ffs on it, then rebuilding will cut down the number of scanned blocks.

It would be interesting to see how skip scans are affected by this as well.

Jared

Hemant K Chitale <hkchital_at_singnet.com.sg> Sent by: ml-errors_at_fatcity.com
11/01/2003 12:34 AM
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        To:        Multiple recipients of list ORACLE-L 
<ORACLE-L_at_fatcity.com> 
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        Subject:        RE: re Rebuilding Indexes in Oracle Apps -- an

update

Richard et al,

{for those who've been following the thread on Rebuilding Indexes ...}

I've just been reading the AskTom thread on rebuilding indexes at
http://asktom.oracle.com/pls/ask/f?p=4950:8:::::F4950_P8_DISPLAYID:6601312252730

and picked on the important line
"Coalesce... reclaim the free space from mostly empty index leaf blocks that will not be reused otherwise due to your increasing sequence. "

Richard has also pointed COALESCE as a better option. COALESCE would be a better option than REBUILD for Indexes on monotonically increasing sequences where older values are purged periodically.

Hemant K Chitale
Oracle 9i Database Administrator Certified Professional My personal web site is : http://hkchital.tripod.com

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