Possible to modify 'substitutability' after creation of a Table of object?

Question

Hello,
I have done:
CREATE TABLE "TOAO" OF "OA"
NOT SUBSTITUTABLE AT ALL LEVELS
... but now I'd like to make this table 'TOAO' SUBSTITUTABLE in order to store child of OA type in, then I tried:
alter table toao substitutable at all levels;
but it doesn't work. How can I do this?
Thank for any clue.
Claude

Answer 1

Hi,
modify_col_substitutable
Use this clause to set or change the substitutability of an existing object type column.
The FORCE keyword drops any hidden columns containing typeid information or data for subtype attributes. You must specify FORCE if the column or any attributes of its type are not FINAL.
Restrictions on Modifying Column Substitutability
          You can specify this clause only once in any ALTER TABLE statement.
          You cannot modify the substitutability of a column in an object table if the substitutability of the table itself has been set.
          You cannot specify this clause if the column was created or added using the IS OF TYPE syntax, which limits the range of subtypes permitted in an object column or attribute to a particular subtype. Please refer to substitutable_column_clause in the documentation on CREATE TABLE for information on the IS OF TYPE syntax.
          You cannot change a varray column to NOT SUBSTITUTABLE, even by specifying FORCE, if any of its attributes are nested object types that are not FINAL.