Connect with Oracle Database.

Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation.  All rights reserved.

C:\Users\rajib.pradhan>sqlplus /nolog

SQL*Plus: Release 11.2.0.1.0 Production on Fri Mar 13 00:39:38 2015

Copyright (c) 1982, 2010, Oracle.  All rights reserved.

SQL> conn /as sysdba
Connected.
SQL> alter user hr identified by hr account unlock;

User altered.

SQL> conn hr/hr
Connected.
SQL> show user
USER is "HR"

SQL>