SQL> startup
ORACLE instance started.

Total System Global Area  538514184 bytes
Fixed Size                   451336 bytes
Variable Size             503316480 bytes
Database Buffers           33554432 bytes
Redo Buffers                1191936 bytes
Database mounted.
ORA-01113: file 26 needs media recovery
ORA-01110: data file 26: '/opt/ora9/product/oradata/NTDB/EXAMPLE02.dbf'
解決方法：

SQL> recover datafile '/opt/ora9/product/oradata/NTDB/EXAMPLE02.dbf'
ORA-00279: change 244674111 generated at 09/24/2013 15:20:41 needed for thread
1
ORA-00289: suggestion : /opt/ora9/product/oracle/dbs/arch1_1123.dbf
ORA-00280: change 244674111 for thread 1 is in sequence #1123

Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
auto
Log applied.
Media recovery complete.
SQL> alter database open;

Database altered.