Oracle Database Search Results: indexing within Performance Tuning Guide

One of the easiest ways to speed up a query is to reduce the number of logical I/Os by eliminating a table access from the execution plan.

A function-based index includes columns that are either transformed by a function, such as the UPPER function, or included in an expression, such as col1 + col2.

Similar to partitioned tables, partitioned indexes improve manageability, availability, performance, and scalability.

An index-organized table differs from an ordinary table in that the data for the table is held in its associated index.

Bitmap indexes can substantially improve performance of queries that have all of the following characteristics:

In addition to a bitmap index on a single table, you can create a bitmap join index, which is a bitmap index for the join of two or more tables.

Domain indexes are built using the indexing logic supplied by a user-defined indextype.

You can use an existing nonunique index on a table to enforce uniqueness, either for UNIQUE constraints or the unique aspect of a PRIMARY KEY constraint.

There are several index types available, and each index has benefits for certain situations.