update_sequence.sql

declare
  l_MaxVal  pls_integer;
  l_Currval pls_integer default - 1;
begin
  -- insert primary key and table name
  select max(cod_os)
    into l_MaxVal
    from os;
  while l_Currval < l_Maxval
  loop
    dbms_output.put_line (l_Currval);
    -- insert sequence name
    select seq_os.nextval
      into l_Currval
      from dual;
  end loop;
end;