Introduction to Using Alternate Indexes

An alternate index provides another way to access a VSAM data set, as described in Keyed Direct Access with an Alternate Index. You define and build alternate indexes by using IBM Access Method Services (AMS).

You can create an alternate index for a new data set or an existing data set, and for an ESDS or a KSDS. An alternate index is itself a KSDS that references the base cluster.

In the following examples, the alternate index enables you to perform direct keyed access of the STUDENT data set by state code. See Sample STUDENT Data Set for the data set that is used in the examples.