ORA-01113: file 13 needs media recovery

oracle@Linux01:[/u01/app/oracle/datafiles/orcl] $ sqlplus /"As sysdba"

SQL*Plus: Release 11.2.0.4.0 Production on Thu Jan 21 10:09:56 2012

Copyright (c) 1982, 2013, Oracle.  All rights reserved.


Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL> ALTER DATABASE
DATAFILE '/u01/app/oracle/datafiles/orcl/USER_DATA_04.dbf'
ONLINE  2 ;

*
ERROR at line 3:
ORA-01916: keyword ONLINE, OFFLINE, RESIZE, AUTOEXTEND or END/DROP expected


SQL> ALTER DATABASE DATAFILE '/u01/app/oracle/datafiles/orcl/USER_DATA_04.dbf' ONLINE;
ALTER DATABASE DATAFILE '/u01/app/oracle/datafiles/orcl/USER_DATA_04.dbf' ONLINE
*
ERROR at line 1:
ORA-01113: file 13 needs media recovery
ORA-01110: data file 13: '/u01/app/oracle/datafiles/orcl/USER_DATA_04.dbf'


SQL> recover datafile '/u01/app/oracle/datafiles/orcl/USER_DATA_04.dbf';
Media recovery complete.
SQL> ALTER DATABASE DATAFILE '/u01/app/oracle/datafiles/orcl/USER_DATA_04.dbf' ONLINE;

Database altered.

SQL>