Angenommen, die Oracle DB (sollte auch für Oracle-XE's SAMPLE funktionieren) ist auf Unix, ssh-in und :
sqlplus /nolog
SQL> connect / as SYSDBA
Connected.
SQL> SELECT username, account_status FROM dba_users WHERE ACCOUNT_STATUS LIKE '%EXPIRED%';
# ... your locked account should be listed ...
SQL> ALTER USER sample IDENTIFIED BY sample;
User altered.
SQL> ALTER USER sample ACCOUNT UNLOCK;
User altered.
SQL> ALTER PROFILE DEFAULT LIMIT PASSWORD_LIFE_TIME UNLIMITED;
Profile altered.
SQL> exit