Oracle Message QSM-02148 - many to many subquery joins require 9.0 compatibility or higher

ERRORmany to many subquery joins require 9.0 compatibility or higher
CAUSEYou have specified a many to many join in your materialized view while running in less than 9.0 compatibility mode.
ACTIONSet your compatibility mode to 9.0 or higher or restructure the materialized view query.