Oracle 11g数据库安装的时候，跳过了密码设置那一项。在后来需要使用sys和system的时候，老是提示密码不对。这里提供一种能重新设置这些用户密码的方法。
使用sqlplus登陆数据库：
bash-3.00$ sqlplus / as sysdba
SQL*Plus: Release 10.2.0.2.0 - Production on Fri Nov 30 16:29:59 2012
Copyright (c) 1982, 2005, Oracle. All Rights Reserved.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.2.0 - Production
With the Partitioning, OLAP and Data Mining options
SQL> alter user sys identified by admin;
User altered.
SQL> conn sys/admin as sysdba;
Connected.
SQL> alter user system identified by admin;
User altered.
至此，你就可以使用自己设置的密码登陆数据库了。