ORA-28000: the account is locked

SQL> conn scott
Enter password:
ERROR:
ORA-28000: the account is locked


Warning: You are no longer connected to ORACLE.
SQL>
SQL> conn sys as sysdba
Enter password:
Connected.
SQL>
SQL>
SQL> alter user scott account unlock;

User altered.

SQL>
SQL>
SQL> alter user scott account unlock identified by tiger;

User altered.

SQL> conn scott
Enter password:
Connected.