just perform a few operations and measure things....
here is an example with indexes...
ops$tkyte%ORA11GR2> create table t
2 as
3 select a.*
4 from all_objects a
5 where 1=0
6 /
Table created.
ops$tkyte%ORA11GR2> create index t_idx1 on t(object_name);
Index created.
ops$tkyte%ORA11GR2> create index t_idx2 on t(object_type);
Index created.
ops$tkyte%ORA11GR2> create index t_idx3 on t(timestamp);
Index created.
ops$tkyte%ORA11GR2>
ops$tkyte%ORA11GR2> connect /
Connected.
ops$tkyte%ORA11GR2> set autotrace on statistics
ops$tkyte%ORA11GR2> insert into t select a.* from all_objects a
2 /
72911 rows created.
Statistics
----------------------------------------------------------
1514 recursive calls
224491 db block gets
57503 consistent gets
888 physical reads
62639584 redo size
902 bytes sent via SQL*Net to client
1011 bytes received via SQL*Net from client
4 SQL*Net roundtrips to/from client
1501 sorts (memory)
0 sorts (disk)
72911 rows processed
ops$tkyte%ORA11GR2> set autotrace off
ops$tkyte%ORA11GR2> @mystat "undo change"
ops$tkyte%ORA11GR2> set echo off
NAME VALUE
----------------------- ----------
undo change vector size 24025452
ops$tkyte%ORA11GR2> commit;
Commit complete.
ops$tkyte%ORA11GR2>
ops$tkyte%ORA11GR2> connect /
Connected.
ops$tkyte%ORA11GR2> set autotrace on statistics
ops$tkyte%ORA11GR2> update t set object_id = object_id+1;
72911 rows updated.
Statistics
----------------------------------------------------------
79 recursive calls
78595 db block gets
1324 consistent gets
112 physical reads
34121652 redo size
902 bytes sent via SQL*Net to client
1004 bytes received via SQL*Net from client
4 SQL*Net roundtrips to/from client
1 sorts (memory)
0 sorts (disk)
72911 rows processed
ops$tkyte%ORA11GR2> set autotrace off
ops$tkyte%ORA11GR2> @mystat "undo change"
ops$tkyte%ORA11GR2> set echo off
NAME VALUE
----------------------- ----------
undo change vector size 22234080
ops$tkyte%ORA11GR2> commit;
Commit complete.
ops$tkyte%ORA11GR2>
ops$tkyte%ORA11GR2> connect /
Connected.
ops$tkyte%ORA11GR2> set autotrace on statistics
ops$tkyte%ORA11GR2> delete from t;
72911 rows deleted.
Statistics
----------------------------------------------------------
423 recursive calls
599516 db block gets
2751 consistent gets
722 physical reads
78043120 redo size
902 bytes sent via SQL*Net to client
981 bytes received via SQL*Net from client
4 SQL*Net roundtrips to/from client
1 sorts (memory)
0 sorts (disk)
72911 rows processed
ops$tkyte%ORA11GR2> set autotrace off
ops$tkyte%ORA11GR2> @mystat "undo change"
ops$tkyte%ORA11GR2> set echo off
NAME VALUE
----------------------- ----------
undo change vector size 40230900
ops$tkyte%ORA11GR2> commit;
Commit complete.