values for mapping of index must be different

  Explanation:   The  data  used  for  a  field  mapping  must  be
  different.   This  message can appear for two reasons:  you used
  the MAPPING VALUES clause in a CREATE INDEX definition and  both
  the high and low values of the range were equal, or you used the
  ALTER INDEX ...  ADD PARTITION statement  and  specified  a  new
  partition  which  matched exactly the WITH LIMIT OF clause of an
  existing partition, or it specified no WITH LIMIT OF clause  and
  matched an existing OTHERWISE partition.

  User Action:  Determine the cause of the problem and correct the
  index definition.