The key definition area describes the keys used in the indexed file.
The key definition area follows the global information area and contains one key definition for each key in the file.
You must define all keys before their components.
The order in which keys are defined is important as the ordinal position of the key is used to identify it. For example, if you have an indexed file with a prime key and two alternate keys, the Key Definition area contains three key definitions: the prime key is key 0, the first alternate is key 1, and the second alternate is key 2.