How To Extend Oracle Database User Expiry Without Changing Existing Password

Step 1) Check the user status

select USERNAME,ACCOUNT_STATUS,LOCK_DATE,EXPIRY_DATE,PROFILE from dba_users where USERNAME='SYSMAN';

Step 2) Fetch the encrypted password for the corresponding user 

select name, password from user$ where name='SYSMAN';

Step 3) Alter the user sysman and set the above encrypted password

alter user SYSMAN identified by values '447B729161192C24' account unlock;

Step 4) Check the user status and try to login using clear text password that your using previously.

select USERNAME,ACCOUNT_STATUS,LOCK_DATE,EXPIRY_DATE,PROFILE from dba_users where USERNAME='SYSMAN';