ORA-01033: ORACLE initialization or shutdown in progress

Error.....
   ORA-01033: ORACLE initialization or shutdown in progress

SQL> conn scott/tiger
ERROR:
ORA-01033: ORACLE initialization or shutdown in
Process ID: 0
Session ID: 0 Serial number: 0
Warning: You are no longer connected to ORACLE.
SQL> exit

Solution.....
C:\Users>sqlplus / as sysdba
SQL*Plus: Release 11.2.0.1.0 Production on Thu Sep 3 18:26:48 2015
Copyright (c) 1982, 2010, Oracle.  All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL> show user
USER is "SYS"
SQL> desc dba_users
ERROR:
ORA-04043: object dba_users does not exist

SQL> shutdown abort;
ORACLE instance shut down.
SQL> startup mount;
ORACLE instance started.
Total System Global Area 3373858816 bytes
Fixed Size                  2180424 bytes
Variable Size            1979714232 bytes
Database Buffers         1375731712 bytes
Redo Buffers               16232448 bytes
Database mounted.
SQL> recover database;
ORA-00283: recovery session canceled due to errors
ORA-00264: no recovery required
SQL> alter database open;
Database altered.
SQL>