Host variable <str> is a vector but is not used as an indicator
  structure

  Explanation:  The host variable is defined as a vector
  (one-dimensional array).  SQL only allows references to vectors
  if they are used as indicator variables for host structures
  (such indicator variables are also called indicator structures
  or indicator vectors).

  User Action:  Either change the host variable declaration so it
  is not an array, or move the data from the array to a variable
  that is not an array.