One of the previous restrictions on materialized views has been removed in Oracle9i
Database Release 2. You can now specify the fast refresh option on a materialized view
utilizing the UNION ALL construct. To determine the table from which a row originates,
since all the rows from each table are present, you use a column, named MARKER , that is
an alphanumeric constant. Each table is assigned a constant value for all rows.
Materialized views can be built on top of this view. For Oracle9i Database Release 2 a
materialized view can be fast refreshable with aggregate functions and joins.
Materialized view logs must be created on all the base tables, using the WITH ROWID option.

What you want to do, is not supported in 9.0.x.

It's a new feature of 9.2.

Hope this helps

Gert