An index can reduce
the time required to locate a set of rows, especially for a large
data file. However, there are costs associated with creating, storing,
and maintaining the index. When deciding whether to create an index,
you must weigh any benefits in performance improvement against the
costs of increased resource usage.
Note: This chapter discusses the benefits and costs that are
associated with using indexes specifically with PROC SQL. To learn
about the costs and benefits of using indexes with other SAS procedures,
see the SAS documentation.