Indexed READ statements transfer input data from external records that have keyed access.
In an indexed file, a series of records can be read in key value sequence by using an indexed READ statement and sequential READ statements. The first record in the sequence is read by using the indexed statement, the rest are read by using the sequential READ statements.
An indexed READ statement can be formatted or unformatted, and takes one of the following forms:
READ (eunit, format, key [,keyid] [,iostat] [,err]) [io-list]
READ (eunit, key [,keyid] [,iostat] [,err]) [io-list]