In the FILE-CONTROL paragraph, you need to define the physical structure of a file and its access mode, as shown below.
FILE-CONTROL.
SELECT file ASSIGN TO FileSystemID-Filename
ORGANIZATION IS org ACCESS MODE IS access.
For org, you can choose SEQUENTIAL (the default), LINE SEQUENTIAL, INDEXED, or RELATIVE.
For access, you can choose SEQUENTIAL (the default), RANDOM, or DYNAMIC.
Sequential and line-sequential files must be accessed sequentially. For indexed or relative files, all three access modes are possible.