parameter concatenation not allowed - check use of plus (+)

  Explanation:  A command that accepts either a single-input value
  for  a  parameter or a list of input values separated by commas,
  contains multiple values concatenated by plus signs ( + ).

  User  Action:   Reenter  the  command   with   a   single   file
  specification.   If  necessary,  enter the command once for each
  file.