an index with this column list already exists

  Explanation:  An index exists with the  same  column  list,  and
  same  type  (either  SORTED  or  HASHED),  with  the same column
  ordering (ASC/DESC)  This  warning  is  intended  to  alert  the
  database administrator that this index may be redundant.

  User Action:  If this index is not needed then drop this  index,
  or  ROLLBACK the CREATE INDEX statement.  If you wish to replace
  an existing index  with  a  different  partitioning  schema  you
  should use ALTER INDEX.  You can also disable the existing index
  using ALTER INDEX ...  MAINTENANCE IS DISABLED so that it is  no
  longer  updated  or  used by queries.  It can then be dropped at
  later time.