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
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Subject:RE: re Rebuilding Indexes in
Oracle Apps -- an updateRichard et al,{for those who've been
following the thread on Rebuilding Indexes ...}I've just been reading
the AskTom thread on rebuilding indexesat
http://asktom.oracle.com/pls/ask/f?p=4950:8:F4950_P8_DISPLAYID:6601312252730and
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
onmonotonically increasing sequences where older values are purged
periodically.Hemant K ChitaleOracle 9i Database Administrator
Certified ProfessionalMy personal web site is :
http://hkchital.tripod.com-- Please see the official
ORACLE-L FAQ: http://www.orafaq.net-- Author: Hemant K
ChitaleINET: [EMAIL PROTECTED]Fat City Network
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Re: re Rebuilding Indexes in Oracle Apps -- an update
Now that I think about it, you're probably right.
I'll test it anyway, I like to see numbers. :)
Jared
Tanel Poder [EMAIL PROTECTED]
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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 [EMAIL PROTECTED]
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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
--
Please see the official ORACLE-L FAQ: http://www.orafaq.net
--
Author: Hemant K Chitale
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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 [EMAIL PROTECTED]
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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
--
Please see the official ORACLE-L FAQ: http://www.orafaq.net
--
Author: Hemant K Chitale
INET: [EMAIL PROTECTED]
Fat City Network Services -- 858-538-5051 http://www.fatcity.com
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To REMOVE yourself from this mailing list, send an E-Mail message
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also send the HELP command for other information (like subscribing).
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
--
Please see the official ORACLE-L FAQ: http://www.orafaq.net
--
Author: Hemant K Chitale
INET: [EMAIL PROTECTED]
Fat City Network Services-- 858-538-5051 http://www.fatcity.com
San Diego, California-- Mailing list and web hosting services
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To REMOVE yourself from this mailing list, send an E-Mail message
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