How to find the redo genrated by DML,DDL

Sometime want to know redo generated by at any transaction  in oracle . We can simply use "  set autotrace on statistics"  

SQL> set autotrace on statistics

SQL> insert into  object1  select * from all_objects;

49951 rows created.

Statistics

----------------------------------------------------------

       6693  recursive calls

       3866  db block gets

      38572  consistent gets

        263  physical reads

    5600712  redo size

        675  bytes sent via SQL*Net to client

        579  bytes received via SQL*Net from client

          4  SQL*Net roundtrips to/from client

         15  sorts (memory)

          0  sorts (disk)

      49951  rows processed

But in few cases create like create Index we can find redo using below quires 

SQL> set verify off

SQL> column value new_val V

SQL> select a.name ,b.value value from v$statname a, v$mystat b  where a.statistic#=b.statistic# and lower(a.name) like '%redo size%' ;

NAME VALUE

---------------------------------------------------------------- ----------

redo size 185164

SQL> create table object3 as select * from dba_objects;

Table created.

SQL> select a.name , b.value ,b.value-&V redogenerated   from v$statname a, v$mystat b where a.statistic#=b.statistic#  and lower(a.name) like '%redo size%';

NAME                         VALUE                     REDOGENERATED  

--------                        ---------                       --------------------

redo size                       239880                        54716

SQL> set verify off

SQL> column value new_val V

SQL> select a.name ,b.value value from v$statname a, v$mystat b

2 where a.statistic#=b.statistic# and lower(a.name) like '%redo size%' ;

NAME VALUE

---------------------------------------------------------------- ----------

redo size 2323044

SQL> create index obind1 on object3(object_type);

Index created.

SQL> select a.name , b.value ,b.value-&V redogenerated

2 from v$statname a, v$mystat b where a.statistic#=b.statistic#

3 and lower(a.name) like '%redo size%';

NAME                  VALUE                   REDOGENERATED    

--------                  ---------                  ------------

   redo size             3503840                   1180796