Re: SAP Reorgs
- From: Jared.Still@xxxxxxxxxxx
- To: oracle-l@xxxxxxxxxxxxx
- Date: Tue, 15 Jun 2004 15:03:44 -0700
> To my opinion reorganizing is OK when , as a result of it, a table or
index
> occupies less data blocks.
> This will, in general, not only cause less LIO for this segment.
Rebuilding a B*Tree index to conserve space can have detrimental effects
on performance.
If the index sees a lot of insert activity, your newly rebuilt index will
undergo block splits, and
soon be back to the size it was previously.
FFS and Range Scans may benefit from a rebuild, but it would probably be
best to
quantify the benefit.
This goes for tables too, dependent on whether or not a table sees many
FTS, and the
access patterns. If straight OLTP, rebuilding to save space may not buy
much performance.
It may take less space in the block buffers, but then again, previously
cool blocks may
become hot.
There are no silver bullets.
See Richard Foote's paper on index internals, it is very informative.
I'm sure he will correct me if I have mis-spoken on any of this. ;)
Jared
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