SQL> show user
USER is "SYS"
SQL> select * from v$version;

BANNER
----------------------------------------------------------------
Oracle Database 10g Enterprise Edition Release 10.1.0.2.0 - Prod
PL/SQL Release 10.1.0.2.0 - Production
CORE 10.1.0.2.0 Production
TNS for 32-bit Windows: Version 10.1.0.2.0 - Production
NLSRTL Version 10.1.0.2.0 - Production

SQL> show parameter audit

NAME TYPE VALUE
------------------------------------ ----------- ---------------
audit_sys_operations boolean FALSE
audit_trail string DB
SQL> audit table ;

Audit succeeded.

SQL> delete from aud$;

5 rows deleted.

SQL> commit;

SQL> conn cmy/cmy;
Connected.
SQL> drop table t;

Table dropped.

SQL> select count(*) from user_audit_trail;

COUNT(*)
----------
1 --------审计成功

偶然发现如果drop table t这句放在toad 8.6版 里面执行，不会生成审计记录！不知道是不是toad的bug.