cannot startup oracle database
815325Jun 21 2011 — edited Jun 23 2011$ sqlplus / as sysdba
SQL*Plus: Release 11.2.0.1.0 Production on Wed Jun 22 08:41:04 2011
Copyright (c) 1982, 2009, Oracle. All rights reserved.
Connected to an idle instance.
SQL> startup
ORACLE instance started.
Total System Global Area 805875712 bytes
Fixed Size 2217672 bytes
Variable Size 239077688 bytes
Database Buffers 562036736 bytes
Redo Buffers 2543616 bytes
Database mounted.
ORA-03113: end-of-file on communication channel
Process ID: 5423
Session ID: 17 Serial number: 3
SQL>
How to fix 'ORA-03113: end-of-file on communication channel' ?
Thanks.