parallel DDL modify column to null

Hello Gurus,

11203

rhel 6

I'm trying to modify an existing column to nullable and its taking a lot of time. Table contains lot of interval/reference partitons and have LOBS,my question is does making a not null column to null should be quick isn't it?  does it need to update the table?

I tried doing following but it still runs in serial mode. How do i make it run in parallel or speed up the operation?

Alter table <table_name> parallel 8;

Alter session force parallel ddl;

Alter table <table_name> modify null; --Your DDL statement.

Alter table <table_name> noparallel