Oracle Message ORA-25106 - only one of PARALLEL or NOPARALLEL clause may be specified

ERRORonly one of PARALLEL or NOPARALLEL clause may be specified
CAUSEPARALLEL was specified more than once, NOPARALLEL was specified more than once, or both PARALLEL and NOPARALLEL were specified in an ALTER INDEX REBUILD statement.
ACTIONRemove all but one of the PARALLEL or NOPARALLEL clauses.