create table big
as
select a.*, rpad('*',1000,'*') data
  from all_objects a;                  
exec dbms_stats.gather_table_stats( user, 'BIG' );
create table small ( x int, y char(500) );
insert into small select rownum, 'x' from all_users;
commit;
exec dbms_stats.gather_table_stats( user, 'SMALL' );
alter system set undo_tablespace = undo_small;
update big
   set temporary = temporary
 where rowid in
(
select r
  from (
select rowid r, row_number() over 
       (partition by dbms_rowid.rowid_block_number(rowid) order by rowid) rn
  from big
       )
 where rn = 1
)
/
commit;
variable x refcursor
exec open :x for select * from big;