field <str> does not exist in this database

  Explanation:  The field that you attempted  to  delete  was  not
  found.   It  might  be a local field in a relation rather than a
  global field.

  User Action:  Check the exact name of the field and try again to
  delete  it.   If  it  is  a local field, use the CHANGE RELATION
  statement to delete the field.