object "<str>" is referenced by <str> (usage:  <str>)

  Explanation:  You attempted to delete a database object, but the
  object  is  used  by  another  object  or  other  definition  as
  described in the message text.

  User Action:   First,  review  the  database  design;  then,  if
  desired,  delete  the  other  definition  which  references this
  object, and then delete this object.