Reactivate Oracle Expired Passwords ORA-28001

This is because password have reached 180 Default limit for Password life time (ORA-28001).

To reset user:

1. Connect to database using any admin users.

2. Execute 
Sql > select * from dba_profiles;
PASSWORD_LIFE_TIME field is responsible for expiring of password after 180 days.

3. Execute following command to disable this feature:
Sql> ALTER PROFILE DEFAULT LIMIT PASSWORD_LIFE_TIME UNLIMITED;

4. Now crosscheck for disabling of this feature.
Sql > select * from dba_profiles;
The value in PASSWORD_LIFE_TIME has changed to unlimited. Now password will never expire.

5. Now change the password of locked user and unlock using following.
sql> alter user [user_name] identified by [password];

sql> alter user [User_name] account unlock;

6. Crosscheck by value of accout_status field in dba_users view.
sql> select username,account_status from dba_users;
The value of account_status filed should by "OPEN" for corresponding user.