（您的阅读是我的荣幸，如有不满之处请留言指正！） sqlplus有几种登陆方式： 1.C: > sqlplus "/as sysdba" --以操作系统权限认证的oracle sys管理员登陆 2.C: > sqlplus /nolog --不在cmd或者terminal当中暴露密码的登陆方式 SQL> conn /as sysdba & SQL> conn sys/password as sysdba 3.C: > sqlplus scott/tiger --非管理员用户登陆 4.C: > sqlplus scott/tiger@orcl --非管理员用户使用tns别名登陆 5.C: > sqlplus sys/password@orcl as sysdba --管理员用户使用tns别名登陆 6.C: > sqlplus --不显露密码的登陆方式 Enter user-name：sys Enter password：password as sysdba --以sys用户登陆的话 必须要加上 as sysdba 子句 但是如果忘记了密码怎么办呢，，，我装oracle的时候就是忘了设置密码了，搜了一下，果然有方法！
一、忘记除SYS、SYSTEM用户之外的用户的登录密码。
用SYS (或SYSTEM)用户登录。
CONN SYS/PASS_WORD AS SYSDBA;
使用如下语句修改用户的密码。
ALTER USER user_name IDENTIFIED BY newpass;
注意：密码不能全是数字。并且不能是数字开头。否则会出现：ORA-00988: 口令缺失或无效
二、忘记SYS用户，或者是SYSTEM用户的密码。
如果是忘记SYSTEM用户的密码，可以用SYS用户登录。然后用ALTER USER 密令
修改密码。
CONN SYS//PASS_WORD AS SYSDBA;
ALTER USER SYSTEM IDENTIFIED BY newpass;
如果是忘记SYS用户的密码，可以用SYSTEM用户登录。然后用ALTER USER 密令
修改密码。
CONN SYSTEM//PASS_WORD ;
ALTER USER SYSTEM IDENTIFIED BY newpass;
三、如果SYS,SYSTEM用户的密码都忘记或是丢失。
这一项尤其重要。
方法一
可以使用ORAPWD.EXE 工具修改密码。
开始菜单->运行->输入‘CMD’,打开命令提示符窗口，输入如下命令：
orapwd file=D:\oracle\product\10.2.0\db_1\database\pwdctcsys.ora
password=newpass
这个命令重新生成了数据库的密码文件。密码文件的位置在ORACLE_HOME目录下
的\database目录下。 这个密码是修改sys用户的密码。除sys和system其他用户的密码不会改变。
方法二
1.如果不记得sys用户的密码了，采用如下方法可以修改密码： (1)打开cmd，输入sqlplus /nolog，回车。
(2)输入“conn / as sysdba”;
2.
(1)在cmd中启动sqlplus；
(2)用sqlplus/as sysdba登录，使其连接到:
Oracle Database 10g Express Edition Release 10.2.0.1.0 - Production
(3)执行ALTER USER DBSNMP ACCOUNT UNLOCK；
(4) 从新用SQL/PLUS登录，设置用户名、密码；
令附图表一张：Oracle 10g 默认用户名/密码
| Username | Password | Description | See Also |
| CTXSYS | CTXSYS | The Oracle Text account | Oracle Text Reference |
| DBSNMP | DBSNMP | The account used by the Management Agent component of Oracle Enterprise Manager to monitor and manage the database | Oracle Enterprise Manager Grid Control Installation and Basic Configuration |
| LBACSYS | LBACSYS | The Oracle Label Security administrator account | Oracle Label Security Administrator's Guide |
| MDDATA | MDDATA | The schema used by Oracle Spatial for storing Geocoder and router data | Oracle Spatial User's Guide and Reference |
| MDSYS | MDSYS | The Oracle Spatial and Oracle interMedia Locator administrator account | Oracle Spatial User's Guide and Reference |
| DMSYS | DMSYS | The Oracle Data Mining account. | Oracle Data Mining Administrator's Guide Oracle Data Mining Concepts |
| OLAPSYS | MANAGER | The account used to create OLAP metadata structures. It owns the OLAP Catalog (CWMLite). | Oracle OLAP Application Developer's Guide |
| ORDPLUGINS | ORDPLUGINS | The Oracle interMedia user. Plug-ins supplied by Oracle and third party format plug-ins are installed in this schema. | Oracle interMedia User's Guide |
| ORDSYS | ORDSYS | The Oracle interMedia administrator account | Oracle interMedia User's Guide |
| OUTLN | OUTLN | The account that supports plan stability. Plan stability enables you to maintain the same execution plans for the same SQL statements. OUTLN acts as a role to centrally manage metadata associated with stored outlines. | Oracle Database Performance Tuning Guide |
| SI_INFORMTN_SCHEMA | SI_INFORMTN_SCHEMA | The account that stores the information views for the SQL/MM Still Image Standard | Oracle interMedia User's Guide |
| SYS | CHANGE_ON_INSTALL | The account used to perform database administration tasks | Oracle Database Administrator's Guide |
| SYSMAN | CHANGE_ON_INSTALL | The account used to perform Oracle Enterprise Manager database administration tasks. Note that SYS and SYSTEM can also perform these tasks. | Oracle Enterprise Manager Grid Control Installation and Basic Configuration |
| SYSTEM | MANAGER | Another account used to perform database administration tasks. |