/sys$common/syshlp/helplib.hlb FORTRAN, Statements, OPEN, ERR  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  ERR = s

  s  Is the label of an executable statement that is to receive
     control when an error occurs.

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