Passando o nome da tabela para o cursor

CREATE OR REPLACE PROCEDURE dynaQuery(
       TAB IN VARCHAR2, 
       sid in number ,
       cur OUT NOCOPY sys_refcursor) IS
 query_str VARCHAR2(200);
BEGIN
    query_str := 'SELECT USERNAME FROM ' || tab
      || ' WHERE sid= :id';
dbms_output.put_line(query_str);
    OPEN cur FOR query_str USING sid;
END ;
/

create table test1(sid number, username varchar2(50));
insert into test1(sid, username) values(123,'abc');
insert into test1(sid, username) values(123,'ddd');
insert into test1(sid, username) values(222,'abc');
commit;
/



 declare 
  cur  sys_refcursor ;
  sid number ;
  uName varchar2(50) ;
  begin
  sid := 123; 
  dynaQuery('test1',sid, cur);
   LOOP
     FETCH cur INTO uName;
     DBMS_OUTPUT.put_line(uName);
     EXIT WHEN cur%NOTFOUND;
     -- process row here
   END LOOP;
CLOSE CUR;


  end ;

SELECT USERNAME FROM test1 WHERE sid= :id
abc
ddd
abc
ddd
ddd