To alter the password expiry policy for a certain user profile in Oracle first check wich profile the user is in using:

select profile from DBA_USERS where username = '<username>';

Then you can change the limit to never expire using:

alter profile <profile_name> limit password_life_time UNLIMITED;

If you want to previously check the limit you may use:

select resource_name,limit from dba_profiles where profile='<profile_name>';

Unlock account :

ALTER USER account IDENTIFIED BY password ACCOUNT UNLOCK;

if user was in grace period, reset password

# if you don't know the password
select spare4 from sys.user$ where name='[user name]';
# reset password
alter user [user name] identified by values '[result from above query]';