NOCOPY

SET SERVEROUTPUT ON;
DECLARE
   n NUMBER := 10;
   PROCEDURE do_something (
      n1 IN NUMBER,
      n2 IN OUT NUMBER,
      n3 IN OUT NOCOPY NUMBER) IS
   BEGIN
      n2 := 20;
      DBMS_OUTPUT.put_line(n1);  -- prints 10
      n3 := 30;
      DBMS_OUTPUT.put_line(n1);  -- prints 30
   END;
BEGIN
   do_something(n, n, n);
   DBMS_OUTPUT.put_line(n);  -- prints 20
END;