Submitted by AbidMalik on Fri, 2011-04-29 14:37
An index created on column that has many duplicated rows can be tuned to save space as well as I/O trips by compressing the index defined on it.
By default when we create index in Oracle, the compression is disabled on it. What if we have an index defined on a column that contains last name of all the customers, some of the names are very common as a last name. We can take advantage of this duplicated data by compressing the index defined on it. This is where the KEY-COMPRESS INDEXES comes in handy.