alter index command

[rswamin]

hello
can anyone tell which is right

when we issue a Alter Index... Rebuild command ,
1) is it the index dropped and then recreated with the same name or
2) a new index is created and then the old one is dropped

if the second case is right then what will be the name of the index. because we cannot have two indexes in the same tablespace with the same name at the same time.

pls clarify

thanks in advance

rswamin

[pando]

a new index is created using either the existing index or table depending on the size of each segment, after the new index is built the old one is dropped that's why you need double disk space when rebuild an index

[slimdave]

To add to that, the previous index cannot be used as the basis for the rebuild if it is "UNUSABLE", of course.