##  Simulating "module version control" via stored 
##  database packages 


    PROCEDURE Upd_Payroll_V10 ( Emp_No IN number) AS
    BEGIN
    ....
    END;

    PROCEDURE Upd_Payroll_V11 ( Emp_No IN number) AS
    BEGIN
    ....
    END;

    PROCEDURE Payroll_V20 AS
       Procedure Upd_Payroll ( Emp_No IN number) AS
       ....
    END;



    PACKAGE Ver_Cntl AS
       Procedure Upd_Payroll ( Emp_No IN number) AS
       ....
    END;

    PACKAGE body Ver_Cntl AS
       Procedure Upd_Payroll ( Emp_No IN number) AS
       BEGIN
          if    fixed.version = 1.0 then
                Upd_Payroll_V10 (Emp_No);
          elsif fixed.version = 1.1 then
                Upd_Payroll_V11 (Emp_No);
          elsif fixed.version = 2.0 then
                Payroll_V20.Upd_Payroll (Emp_No);
          else
                raise_application_error (-20001, ‘.....’);
          end_if;
       END;
      ....
      ....
    END;


    BEGIN
      ....
      Ver_Cntl.Upd_Payroll ( 12345 );
      ....
    END;