Identifies a branch target statement that receives control if an
  error occurs.  It takes the following form:

  ERR = s

  s  Is the label of an executable statement

  ERR applies only to the OPEN statement in which it is specified,
  and not in subsequent I/O operations on the unit.  If an error
  occurs, no file is opened or created.  However, you can use IOSTAT
  in subsequent I/O statements to perform a similar function.