一、忘記除SYS、SYSTEM用戶之外的用戶的登錄密碼。
用SYS (或SYSTEM)用戶登錄。
CONN SYS/PASS_WORD AS SYSDBA;
使用如下語句修改用戶的密碼。
ALTER USER user_name IDENTIFIED BY newpass;
注意：密碼不能全是數字。並且不能是數字開頭。否則會出現：ORA-00988: 口令缺失或無效
二、忘記SYS用戶，或者是SYSTEM用戶的密碼。
如果是忘記SYSTEM用戶的密碼，可以用SYS用戶登錄。然後用ALTER USER 密令
修改密碼。
CONN SYS//PASS_WORD AS SYSDBA;
ALTER USER SYSTEM IDENTIFIED BY newpass;
如果是忘記SYS用戶的密碼，可以用SYSTEM用戶登錄。然後用ALTER USER 密令
修改密碼。
CONN SYSTEM//PASS_WORD ;
ALTER USER SYSTEM IDENTIFIED BY newpass;
三、如果SYS,SYSTEM用戶的密碼都忘記或是丟失。
這一項尤其重要。
方法一、
可以使用ORAPWD.EXE 工具修改密碼。
開始菜單->運行->輸入‘CMD’,打開命令提示符窗口，輸入如下命令：
orapwd file=D:\oracle\product\10.2.0\db_1\database\pwdctcsys.ora
password=newpass
這個命令重新生成了數據庫的密碼文件。密碼文件的位置在ORACLE_HOME目錄下
的\database目錄下。 這個密碼是修改sys用戶的密碼。除sys和system其他用戶的密碼不會改變。
方法二、
1.如果不記得sys用戶的密碼了，採用如下方法可以修改密碼：
(1)打開cmd，輸入sqlplus /nolog，回車。
(2)輸入“conn / as sysdba”;
(3)輸入“alter user sys identified by 新密碼;”（新密碼必須以字母開頭，另外每條SQL語句後得分號不能忘）
其他用戶方式同理
2.(1)在cmd中啓動sqlplus；
(2)用sqlplus/as sysdba登錄，使其連接到:
OracleDatabase 10g Express Edition Release 10.2.0.1.0 - Production
(3)執行ALTER USER DBSNMP ACCOUNT UNLOCK；
(4) 從新用SQL/PLUS登錄，設置用戶名、密碼；
附：Oracle10g 默認安裝帶來的用戶名/密碼
Username | Password | Description | See Also |
CTXSYS | CTXSYS | The OracleText account | OracleText Reference |
DBSNMP | DBSNMP | The account used by the Management Agent component of OracleEnterprise Manager to monitor and manage the database | OracleEnterprise Manager Grid Control Installation and Basic Configuration |
LBACSYS | LBACSYS | The OracleLabel Security administrator account | OracleLabel Security Administrator's Guide |
MDDATA | MDDATA | The schema used by OracleSpatial for storing Geocoder and router data | OracleSpatial User's Guide and Reference |
MDSYS | MDSYS | The OracleSpatial and OracleinterMedia Locator administrator account | OracleSpatial User's Guide and Reference |
DMSYS | DMSYS | The OracleData Mining account. | OracleData Mining Administrator's Guide OracleData Mining Concepts |
OLAPSYS | MANAGER | The account used to create OLAP metadata structures. It owns the OLAP Catalog (CWMLite). | OracleOLAP Application Developer's Guide |
ORDPLUGINS | ORDPLUGINS | The OracleinterMedia user. Plug-ins supplied by Oracleand third party format plug-ins are installed in this schema. | OracleinterMedia User's Guide |
ORDSYS | ORDSYS | The OracleinterMedia administrator account | OracleinterMedia 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. | OracleDatabase Performance Tuning Guide |
SI_INFORMTN_SCHEMA | SI_INFORMTN_SCHEMA | The account that stores the information views for the SQL/MM Still Image Standard | OracleinterMedia User's Guide |
SYS | CHANGE_ON_INSTALL | The account used to perform database administration tasks | OracleDatabase Administrator's Guide |
SYSMAN | CHANGE_ON_INSTALL | The account used to perform OracleEnterprise Manager database administration tasks. Note that SYS and SYSTEM can also perform these tasks. | OracleEnterprise Manager Grid Control Installation and Basic Configuration |
SYSTEM | MANAGER | Another account used to perform database administration tasks. |