ARCHIVELOG versus NOARCHIVELOG mode

First, we have create the folowing procedure to print redo log size generated for a period :

create table last_redo_size as select value redo_size
from v$sysstat where name = 'redo size';

create or replace package redo_diff as
procedure diff_it;
end;
/

create or replace package body redo_diff as
s number;

function get_size return number is
s_ number;
begin
select value into s_ from sys.v_$sysstat where name = 'redo size';
return s_;
end get_size;

procedure diff_it is
s_new number;
begin
s_new := get_size;
dbms_output.put_line('redo diff: ' || to_char(s_new - s));