How to trace drop command in oracle database.

Question

Dear All,
As a DBA how can we trace the drop cammand in database to know who droped , deleted the tables or deleted data from tables or droped directory from dba_directories.
Thanks,

Answer 1

Thanks Kamran,
see for me audit file is not creating at OS level.
SQL> CONN audit_test/password
Connected.
SQL>
SQL> CREATE TABLE test_tab (id NUMBER 3 );
Table created.
SQL>
SQL> INSERT INTO test_tab (id) VALUES (1);
1 row created.
SQL> UPDATE test_tab SET id = id;
1 row updated.
SQL> SELECT * FROM test_tab;
ID
1
SQL> DELETE FROM test_tab;
1 row deleted.
SQL> DROP TABLE test_tab;
Table dropped.
SQL> conn /as sysdba
Connected.
SQL> show parameter audit
NAME TYPE VALUE
audit_file_dest string C:\ORACLE\PRODUCT\10.2.0\ADMIN
\TEST1\ADUMP
audit_sys_operations boolean TRUE
audit_trail string OS
SQL> host
Microsoft Windows XP [Version 5.1.2600]
(C) Copyright 1985-2001 Microsoft Corp.
C:\Documents and Settings\sherkhan>cd c:\oracle\product\10.2.0\admin\test1\adump
C:\oracle\product\10.2.0\admin\test1\adump>dir
Volume in drive C has no label.
Volume Serial Number is F855-F548
Directory of C:\oracle\product\10.2.0\admin\test1\adump
05/19/2011 09:07 AM <DIR> .
05/19/2011 09:07 AM <DIR> ..
0 File(s) 0 bytes
2 Dir(s) 1,414,656,000 bytes free
Thankss