Question

Oracle Database 11g: Invisible Indexes

Answer 1

Oracle 11g allows indexes to be marked as invisible. 

Invisible indexes are maintained like any other index, but they are ignored by the optimizer unless the OPTIMIZER_USE_INVISIBLE_INDEXES parameter is set to TRUE at the instance or session level. Indexes can be created as invisible by using the INVISIBLE keyword, and their visibility can be toggled using the ALTER INDEX command.

CREATE INDEX index_name ON table_name(column_name) INVISIBLE;

ALTER INDEX index_name INVISIBLE;
ALTER INDEX index_name VISIBLE;

Invisible indexes can be useful for processes with specific indexing needs, where the presence of the indexes may adversely affect other functional areas. They are also useful for testing the impact of dropping an index.

The current visibility status of an index is indicated by the VISIBILITY column of the [DBA|ALL|USER]_INDEXES views.