Changing a materialized view column's length after a change in the base table? We changed the underlying table column size (length). So the materialized view which is built on that table throws an error now since the MV column still has the old size.

This is an Oracle 11gR2 database.

How can I change the MV column's length to match the table's new column size without dropping the MV and recreating it?
You have to drop and recreate.

If you look at the documentation here, you can see that only modification of the storage clauses are allowed.