通过我们可以通过dd来完成这个操作，我们还可以使用rman来操作：

[oracle@10g hcl]$ rman target /

Recovery Manager: Release 10.2.0.1.0 - Production on Tue Nov 4 13:12:31 2008

Copyright (c) 1982, 2005, Oracle. All rights reserved.

connected to target database: TEST (DBID=1963002549)

RMAN> sql 'alter database datafile 5 offline';

using target database control file instead of recovery catalog
sql statement: alter database datafile 5 offline

RMAN> backup as copy datafile 5 format '/home/oracle/oradata/test/ts.dbf';

Starting backup at 04-NOV-08
using channel ORA_DISK_1
channel ORA_DISK_1: starting datafile copy
input datafile fno=00005 name=/home/oracle/oradata/test/ts01.dbf
output filename=/home/oracle/oradata/test/ts.dbf tag=TAG20081104T131307 recid=3 stamp=669906788
channel ORA_DISK_1: datafile copy complete, elapsed time: 00:00:01
Finished backup at 04-NOV-08

RMAN> switch datafile 5 to copy;

datafile 5 switched to datafile copy "/home/oracle/oradata/test/ts.dbf"

RMAN> sql 'alter database datafile 5 online';

sql statement: alter database datafile 5 online

RMAN> exit