Access modes

See the descriptions of the following types of access modes.

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.