List users

set pages 999 lines 100
col username	format a20
col status	format a8
col tablespace	format a20
col temp_ts	format a20
select	username
,	account_status status
,	created
,	default_tablespace tablespace
,	temporary_tablespace temp_ts
from	dba_users
order	by username
/

Lock or unlock a user

alter user <username> account lock;

alter user <username> account unlock;