When indexed file organization is used, the position of each logical record in the file is determined by indices which are generated with the file and are maintained by the system. These indices are based on keys which must be supplied by the user in the records. Indexed files must be assigned to disk storage devices.
The RECORD KEY clause must be specified when creating an indexed file. This clause defines which data item within the record is to be used as the primary key.
The ALTERNATE RECORD KEY clause can be used to define one or more alternate keys (secondary keys) in addition to the primary key.
The START statement can be used to define a starting point, within an indexed file, for a series of subsequent sequential access operations.