oracle - What are the differences between 'shrink space compact' and 'coalesce'? -


the oracle documentation says during altering index clauses shrink space compact , coalesce quite similar , replaced each other, tom found differences in behavior.

since coalesce not available in standart edition of oracle database, suppose there're benefits in using it.

so, differences? can perform shrink space compact on dynamically changing index?

first of all, indexes not need rebuilt. grow steady size , stay there, , rebuilding them produces temporary benefit queries counterbalanced increased load in modifying them due increased rate of block splits. don't forget best optimisation process eliminate -- if think have need frequent rebuilds post question , maybe cause can explained , different approach found.

anyway, coalesce reduces number of blocks holding index data, freeing blocks can re-used new index entries. freed blocks still allocated index, though. can prevent indexes growing large.

shrink similar moves populated blocks allow freed blocks @ "end" of index segment deallocated it. index segment gets smaller. requires exclusive lock on table.


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