rob@XE:11g2> SELECT name, value, isdefault FROM v$parameter

  2  WHERE name LIKE 'undo%';

NAME                VALUE               ISDEFAULT

==================  ==================  =========

undo_management     AUTO                TRUE

undo_tablespace     UNDOTBS_01          FALSE

undo_retention      900                 TRUE

rob@XE:11g2> GRANT FLASHBACK ANY TABLE TO rob;

Grant succeeded.

rob@XE:11g2> ALTER TABLE test_deleting ENABLE ROW MOVEMENT;

Table altered.

rob@XE:11g2> @scn

       SCN TIMEPOINT

~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~

  29719987 2013-03-23 18:24:47

rob@XE:11g2> DELETE FROM test_deleting X

  2  WHERE batch_id = 2002 AND X.rowid <>

  3  (SELECT MAX(Y.rowid) FROM test_deleting Y

  4  WHERE Y.alpha_code = X.alpha_code

  5  AND Y.num_code = X.num_code);

13150 rows deleted.

rob@XE:11g2> SELECT COUNT(*) FROM test_deleting;

  COUNT(*)

~~~~~~~~~~

    446850

rob@XE:11g2> COMMIT;

rob@XE:11g2> @scn

       SCN TIMEPOINT

~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~

  29720004 2013-03-23 18:25:59

rob@XE:11g2> FLASHBACK TABLE test_deleting TO SCN 29719987;

Flashback complete.

rob@XE:11g2> SELECT COUNT(*) FROM test_deleting;

  COUNT(*)

~~~~~~~~~~

    460000

rob@XE:11g2> ALTER TABLE test_deleting DISABLE ROW MOVEMENT;

Table altered.