1.首先使用操作系统方式认证登陆SYS账户，修改SYSTEM账户密码。
$ sqlplus / as sysdba
SQL*Plus: Release 11.2.0.4.0 Production on Fri Mar 20 14:23:41 2015
Copyright (c) 1982, 2013, Oracle. All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
?With the Partitioning, Real Application Clusters, Automatic Storage Management, OLAP,
?Data Mining and Real Application Testing options
?
?SQL> show user;
?USER is "SYS"
?SQL> alter user SYSTEM identified by "oracle123";
?
?User altered.
?
?SQL> exit
2.使用SQLPLUS远程登录方式登陆SYSTEM账户，修改SYS账户密码。
$ sqlplus SYSTEM@orcl
SQL*Plus: Release 11.2.0.4.0 Production on Fri Mar 20 14:22:35 2015
Copyright (c) 1982, 2013, Oracle. All rights reserved.
Enter password:
Connected to:
?Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
?With the Partitioning, Real Application Clusters, Automatic Storage Management, OLAP,
?Data Mining and Real Application Testing options
?
?SQL> show user;
?USER is "SYSTEM"
?SQL> alter user SYS identified by "Oracle123";
?
?User altered.?
?SQL> exit
至此，大功告成，使用远程登录方式尽情登陆吧~