1、修改前做好参数文件的备份
[oracle@pttestdbby1 ~]$ sqlplus / as sysdba

SQL*Plus: Release 10.2.0.5.0 - Production on Tue Nov 11 08:54:45 2014

Copyright (c) 1982, 2010, Oracle. All rights reserved.


Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.5.0 - 64bit Production
With the Partitioning, oracle Label Security, OLAP, Data Mining Scoring Engine 
and Real Application Testing options

SQL> show parameter pfile

NAME                                TYPE        VALUE
------------------------------------ ----------- ------------------------------
spfile                              string      /u01/app/oracle/product/10.2.0
                                                /dbs/spfileZYJY75.ora

SQL> create pfile from spfile;

File created.

2、执行下面的命令
alter system set audit_trail=NONE scope=spfile;
由于audit_trail是动态参数，必须在后面加scope=spfile，重启库生效

3、关闭数据库
SQL> shutdown immediate

4、启动实例
SQL> startup

5、查看审计功能是否关闭
[oracle@pttestdbby1 ~]$ sqlplus / as sysdba

SQL*Plus: Release 10.2.0.5.0 - Production on Tue Nov 11 09:12:45 2014

Copyright (c) 1982, 2010, Oracle. All rights reserved.


Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.5.0 - 64bit Production
With the Partitioning, oracle Label Security, OLAP, Data Mining Scoring Engine 
and Real Application Testing options

SQL> show parameter audit

NAME                                TYPE        VALUE
------------------------------------ ----------- ------------------------------
audit_file_dest                     string      /u01/app/oracle/admin/ZYJY75/a
                                                dump
audit_sys_operations                boolean     FALSE
audit_syslog_level                  string
audit_trail                         string      NONE

ok已经为NONE了，此时审计功能已经关闭了。