ALternate Index provides an additional path to access the Vsam file.
While declaring an alternate index the characteristics of the alternate key to be considered is stated.
The path provides a physical path to relate the Alternate Index with the Main cluster.
Physically records are populated into the alternate Index file when this step is carried out.Each alternate key is associated with one or multiple main keys.
The main purpose of AIX is to access the same file in multiple ways without creating separate copies.
In the program the file can be accessed using the alternate index in the same manner as primary index.AIX key should be declared initially.