step 1  tablespace offline

alter tablespace tablespacename offline;

step 2 datafile offline

alter database datafile '$DatafilePath/datafilename' offline

step 3 use rman tools move datafile

rman target /

RMAN> copy datafile '$oldPath/datafilename'  to '$newpath/rm_dat_ts1_01.dbf';
Starting backup at 2014-04-03 18:52:41
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=637 instance=**** device type=DISK
channel ORA_DISK_1: starting datafile copy
input datafile file number=00032 name=+DATA/*****.dbf
output file name=+DATA2/coredb/datafile/rm_dat_ts1_01.dbf tag=TAG20140403T185243 RECID=1 STAMP=843936775
channel ORA_DISK_1: datafile copy complete, elapsed time: 00:00:15
Finished backup at 2014-04-03 18:52:58

step 4 rename datafile

RMAN> run {
2> set newname for datafile '$oldPath/datafilename'  to '$newpath/rm_dat_ts1_01.dbf';;
3> switch datafile all;
4> }

step 5 online datafile

alter database datafile '$NewPath/datafilename' online;

step 6 online tablespace

alter tablespace tablespacename online;