有一个库，由于设置了PASSWORD_LIFE_TIME，且到期未重置密码，账户被锁了，手工解锁后，登录发现报错ORA-28002，明明解锁了，为何还会报错？
ORA-28002是一个很简单的错误号，
oerr ora 28002
28002, 00000, "the password will expire within %s days"
// *Cause: The user's account is about to about to expire and the password needs to be changed
// *Action: change the password or contact the DBA
可以分为两个场景说明，首先创建profile和用户t_pro_user，其中PASSWORD_LIFE_TIME设置为1，表示密码只有1天有效期，然后将其赋予t_pro_user用户，
SQL> create profile t_profile limit PASSWORD_LIFE_TIME 1;
Profile created.
SQL> create user t_pro_user identified by 123;
User created.
SQL> alter user t_pro_user profile t_profile;
User altered.
grant resource,connect to t_pro_user;
Grant succeeded.
场景一：超过PASSWORD_LIFE_TIME，未更改此值前就登录一次，会报ORA-28002
1天之后，登录就会提示，ORA-28002错误，警告密码7天内就会过期，
sqlplus t_pro_user/123
SQL*Plus: Release 11.2.0.4.0 Production on Mon Sep 18 12:03:16 2017
Copyright (c) 1982, 2013, Oracle. All rights reserved.
ERROR:
ORA-28002: the password will expire within 7 days
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL>
注意：这里提示了7天，是由profile中的PASSWORD_GRACE_TIME参数控制的，默认值是7，表示密码过期之后还有多少天可以使用原密码。
此时将PASSWORD_LIFE_TIME设置为unlimited，
SQL> alter profile t_profile limit PASSWORD_LIFE_TIME unlimited;
Profile altered.
再次登录，提示相同的错误，
sqlplus t_pro_user/123
SQL*Plus: Release 11.2.0.4.0 Production on Mon Sep 18 12:03:16 2017
Copyright (c) 1982, 2013, Oracle. All rights reserved.
ERROR:
ORA-28002: the password will expire within 7 days
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL>
手工修改一次新密码，
SQL> alter user t_pro_user identified by 123;
User altered.
再次登录，就不会报错了，
sqlplus t_pro_user/123
SQL*Plus: Release 11.2.0.4.0 Production on Mon Sep 18 12:04:01 2017
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, OLAP, Data Mining and Real Application Testing options
场景二：超过PASSWORD_LIFE_TIME，但不登录，直接改此参数，再次登录，不会报ORA-28002
1天之后，不登录直接修改PASSWORD_LIFE_TIME，
SQL> alter profile t_profile limit PASSWORD_LIFE_TIME unlimited;
Profile altered.
再次登录，此时未有提示ORA-28002，
sqlplus t_pro_user/123
SQL*Plus: Release 11.2.0.4.0 Production on Mon Oct 2 17:38:37 2017
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, OLAP, Data Mining and Real Application Testing options
其实，这篇MOS文章《ORA-28002 Even If Default Profile Has Limits Set To 'UNLIMITED' (文档 ID 292093.1)》有相关介绍，
if we reset the default profile to have all the limits unlimited and set PASSWORD_VERIFY_FUNCTION to NULL, the restriction are still there because of the previous settings. Resetting the profile parameters is not enough.
如果PASSWORD_VERIFY_FUNCTION to NULL参数设置为NULL，不能仅仅依靠重新设置PASSWORD_LIFE_TIME参数。
If we change the password of the user(s) having default profile now (with PASSWORD_VERIFY_FUNCTION set to NULL), then the error ORA-28002 will not come. This is as expected because of the error ORA-28002. We can change the password of the user(s) to the same existing one.
PASSWORD_VERIFY_FUNCTION to NULL参数设置为NULL，修改了用户的密码，就不会报错ORA-28002，这也是ORA-28002错误期望的结果，当然允许设置重复的密码，重要的不是密码是什么，而是重新设置了一次。
For example:
ALTER PROFILE DEFAULT LIMIT PASSWORD_VERIFY_FUNCTION null;
alter user scott identified by tiger;
( alter user <username> identified by <same password>; )
总结：
1. 如果用户密码超过了PASSWORD_LIFE_TIME的值，未被提示ORA-28002之前对PASSWORD_LIFE_TIME进行了修改，再次登录，不会提示ORA-28002。
2. 如果用户密码超过了PASSWORD_LIFE_TIME的值，曾经登陆过并被提示ORA-28002，此时PASSWORD_LIFE_TIME进行了修改，再次登录，仍会提示ORA-28002，必须手工再改一次密码，才能消除此错。重新设置密码，这是ORA-28002错误的初衷。
对于ORA-28000错误，应该和上述两个结论一致，有兴趣可以试试。
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