ASA SQL User's Guide
Working with Database Objects
Working with indexes
Choosing an appropriate set of indexes for a database is an important part of optimizing performance. Identifying an appropriate set can also be a demanding problem. The performance benefits from some indexes may be significant, but there are also costs associated with indexes, in both storage space and in overhead when modifying data.
The Index Consultant is a tool to assist you in proper selection of indexes. It analyzes either a single query or a set of operations, and recommends which indexes to add to your database. It also notifies you of indexes that are unused.
For more information about the Index Consultant, see Starting the Index Consultant.