可以参考如下方法在忘记oracle密码的情况下，修改密码。
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忘记sys，system用户的密码：
使用ORAPWD.EXE工具修改密码：在开始菜单点击‘运行’，输入‘cmd’，打开命令提示窗口，输入如下命令：
orapwd file=d:\oracle\product\10.1.0\Db_2\database\pwdctcsys.ora password=123456
这个命令重新生成了数据库密码文件。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。 除了sys和system其它用户的密码不会改变。
忘记system用户的密码：
可以用sys用户登录。然后用alter user命令修改密码。如：
conn sys/pass_word as sysdba;
alter user system identified by newpass;
忘记sys用户密码：
可以用system用户登录。然后用alert user 命令修改密码，如：
CONN SYSTEM/PASS_WORD;
ALTER USER SYSTEM IDENTIFIED BY NEWPASS;
忘记除sys/system用户之外的用户的登录密码。
用sys（或者system）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;主要密码不能是全数字且不能以数字开头。
(1)CONN SYS/PASS AS SYSDBA;//以DBA的身份登录
在sql
puls里请输入用户名中输入：sys/sys
as
sysdba
注意：这里的第二sys是密码
可以填其他的
然后对你需要进的用户修改密码：alter
user
用户名
identified
by
密码;
对于oracle10g来说：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”;
(3)输入“alter user sys identified by 新密码;”（新密码必须以字母开头，另外每条SQL语句后得分号不能忘）
其他用户方式同理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； 附：Oracle 10g 默认安装带来的用户名/密码 UsernamePasswordDescriptionSee AlsoCTXSYSCTXSYSThe Oracle Text accountOracle Text ReferenceDBSNMPDBSNMPThe account used by the Management Agent component of Oracle Enterprise Manager to monitor and manage the databaseOracle Enterprise Manager Grid Control Installation and Basic ConfigurationLBACSYSLBACSYSThe Oracle Label Security administrator accountOracle Label Security Administrator's GuideMDDATAMDDATAThe schema used by Oracle Spatial for storing Geocoder and router dataOracle Spatial User's Guide and ReferenceMDSYSMDSYSThe Oracle Spatial and Oracle interMedia Locator administrator accountOracle Spatial User's Guide and ReferenceDMSYSDMSYSThe Oracle Data Mining account.Oracle Data Mining Administrator's GuideOracle Data Mining ConceptsOLAPSYSMANAGERThe account used to create OLAP metadata structures. It owns the OLAP Catalog (CWMLite).Oracle OLAP Application Developer's GuideORDPLUGINSORDPLUGINSThe Oracle interMedia user. Plug-ins supplied by Oracle and third party format plug-ins are installed in this schema.Oracle interMedia User's GuideORDSYSORDSYSThe Oracle interMedia administrator accountOracle interMedia User's GuideOUTLNOUTLNThe 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 GuideSI_INFORMTN_SCHEMASI_INFORMTN_SCHEMAThe account that stores the information views for the SQL/MM Still Image StandardOracle interMedia User's GuideSYSCHANGE_ON_INSTALLThe account used to perform database administration tasksOracle Database Administrator's GuideSYSMANCHANGE_ON_INSTALLThe 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 ConfigurationSYSTEMMANAGERAnother account used to perform database administration tasks.