ERROR - An OPEN statement contains a key specification that is not  an
  unsubscripted  WORD,  LONGWORD,  DECIMAL, STRING, or a RECORD or GROUP
  exactly  8  bytes  long.   Change  the  key  specification  to  be  an
  unsubscripted  WORD,  LONGWORD,  DECIMAL,  STRING or a RECORD or GROUP
  exactly 8 bytes long.