9i allows you to force all statements within a current session to be issued in parallel using the command
ALTER SESSION FORCE PARALLEL DML|DDL|QUERY
Whilst the usefulness of the command may appear limited, consider the common task of copying a schema from one database to another via export/import. After the tables have been loaded, the next step is typically to create the indexes.
In the past, the indexfile would have been manually edited to add appropriate PARALLEL clauses to speed up the process. Now its far simpler process - the storage clauses do not need to be edited. You just issue:
ALTER SESSION FORCE PARALLEL DDL PARALLEL 5;