To move datafile from one disk group to another you need to follow these steps

To move datafile from one disk group to another you need to follow these steps:

1-Identify datafiles that will be moved:
SQL>select
file_name
from
dba_data_files;

2-Identify the disk group destination
--Connect to ASM instance
SQL> select
name
from
v$asm_diskgroup;

3-Take the datafile OFFLINE
SQL>alter database datafile 'file_name' offline;

4-Copy the file using either dbms_file_transfer or RMAN:
--DBMS_FILE_TRANSFER
begin
dbms_file_transfer.copy_file(
source_directory_object => 'DIR_ORIG', --This is an object directory created pointing to original datafile location
source_file_name => 'Data_File_Name.dbf',
destination_directory_object => 'DIR_DEST', --This is an object directory pointing to destination of datafile
destination_file_name => 'Data_File_Name_New.dbf');
end;

--RMAN
RMAN>copy datafile '+DG_ORIG/dbname/datafiles/Data_File_Name.dbf' TO '+DB_DEST';

5-Rename the datafile
SQL alter database rename file '+DG_ORIG/dbname/datafiles/Data_File_Name.dbf' to '+DG_DEST/db_name/datafiles/Data_File_Name_New.dbf'

6-Recover the datafile
SQL>recover datafile '+DG_DEST/db_name/datafiles/Data_File_Name_New.dbf';

7-Put the datafile ONLINE
SQL>alter database datafile '+DG_DEST/db_name/datafiles/Data_File_Name_New.dbf' online;

8-Delete the old datafile using ASMCMD
ASMCMD> cd +DG_ORIG/dbname/datafiles/
ASMCMD> rm -rf Data_File_Name.dbf

9-Backup your tablespace or your database


Best Regards,
Paulo Portugal