RE: re Rebuilding Indexes in Oracle Apps -- an update

> COALESCE would be a better option than REBUILD for Indexes on
> monotonically increasing sequences where older values are purged
periodically.

Unless you happen to be doing index_ffs on that particular index, in which

case a rebuild *may* be in order. Rebuilding the index may cause insert performance problems for a time due to block splits.

If the index is a composite index with some other non-unique value(s) making up the index, a higher than normal number of block splits may be in your future. I haven't tested the composite index yet, but this seems reasonable.

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
 Please respond to ORACLE-L  

        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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