- Sequential-access mode
- Allows reading and writing records of a file in a serial manner; the order of
reference is implicitly determined by the position of a record in the file.
- Random-access mode
- Allows reading and writing records in a programmer-specified manner; the control of
successive references to the file is expressed by specifically defined keys supplied by
the user.
- Dynamic-access mode
- Allows the specific input-output statement to determine the access mode. Therefore,
records can be processed sequentially or randomly or both.
For external files, every file-control entry in the run unit that is associated with
that external file must specify the same access mode. In addition, for relative file
entries, data-name-4 must reference an external data item, and the RELATIVE KEY phrase
in each associated file-control entry must reference that same external data item.