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.
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