[oracle@jumper eygle]$ sqlplus "/ as sysdba"
SQL*Plus: Release 9.2.0.4.0 - Production on Sun Aug 20 01:22:50 2006
Copyright (c) 1982, 2002, Oracle Corporation. All rights reserved.
Connected to an idle instance.
SQL> startup mount
ORACLE instance started.
Total System Global Area 252777592 bytes
Fixed Size 451704 bytes
Variable Size 134217728 bytes
Database Buffers 117440512 bytes
Redo Buffers 667648 bytes
Database mounted.

SQL> alter database open;
alter database open
*
ERROR at line 1:
ORA-01157: cannot identify/lock data file 3 - see DBWR trace file
ORA-01110: data file 3: '/opt/oracle/oradata/eygle/eygle02.dbf'

SQL> alter database create datafile 3 as '/opt/oracle/oradata/eygle/eygle02.dbf';
Database altered.
SQL> select name from v$datafile;
NAME
-------------------------------------------------------
/opt/oracle/oradata/eygle/system01.dbf
/opt/oracle/oradata/eygle/undotbs01.dbf
/opt/oracle/oradata/eygle/eygle02.dbf
/opt/oracle/oradata/eygle/eygle01.dbf
SQL> alter database open;
alter database open
*
ERROR at line 1:
ORA-01113: file 3 needs media recovery
ORA-01110: data file 3: '/opt/oracle/oradata/eygle/eygle02.dbf'

SQL> recover datafile 3;
Media recovery complete.
SQL> alter database open;
Database altered.
SQL>