Message Oracle ORA-29921 - Ancillary operator not supported with set view query block

ERRORAncillary operator not supported with set view query block
CAUSEOuter view query block contains ancillary operator and view query block contains union all.
ACTIONDefine the union-all view query to contain the primary and ancillary query terms. i.e. have the operators within the view definition rather than in the query outside the view.