Oracle index reorganize architecter

hi all,
normaly we all know oracle index rebuild means drop index and created it again. I want to know what is index reorganizeing is? And after index reorganize happpen what is the storage level behind macanisum? And how is that(index reorganize) effected in DB blok, segments ,extentd and table space level?
Thank you
Tharindu Dhaneenja

Dhaneenja wrote:
hi all,
normaly we all know oracle index rebuild means drop index and created it again. I want to know what is index reorganizeing is? And after index reorganize happpen what is the storage level behind macanisum? And how is that(index reorganize) effected in DB blok, segments ,extentd and table space level?
Technically Oracle's rebuild command creates a new copy of the index then drops the old copy. The reason for splitting hairs about this is that Oracle does not have a definition of "reorganizing" an index - so we need to have the context in which you saw the term so that we can decide what the author intended.
There is a coalesce command that moves index entries from one leaf block to another in order to get some leaf blocks well-packed and make others completely free. Since this is a delete/insert operation it generates a lot of undo and redo.
There are also two versions of the "shrink" command that play similar games.
Rebuild, and "shrink space" can result in less space being allocated in the tablespace for the final state of the index; "shrink space compact" and coalesce don't move the index segment at all, and don't free any space back to the tablespace.
Regards
Jonathan Lewis

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Message was edited by:
lytaylor
Message was edited by:
lytaylor

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