Indicates the allowed I/O operations for the file connection.  It
  takes the following form:

  ACTION = act

  act  Is a character expression with one of the
       following values:

  'READ'      Indicates that only READ statements can refer to
              this connection.
  'WRITE'     Indicates that only WRITE, DELETE, and ENDFILE
              statements can refer to this connection.
  'READWRITE' Indicates that READ, WRITE, DELETE, and ENDFILE
              statements can refer to this connection (*DEFAULT*)