rman: RMAN-10015: error compiling PL/SQL program

RMAN> sql "alter database datafile '/u01/app/oracle/oradata/orcl/test_1.dbf' off line";

using target database control file instead of recovery catalog
sql statement: alter database datafile '/u01/app/oracle/oradata/orcl/test_1.dbf' offline
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03009: failure of sql command on default channel at 09/06/2010 13:18:57
RMAN-10015: error compiling PL/SQL program

SQL> alter database datafile '/u01/app/oracle/oradata/orcl/test_1.dbf' offline;
alter database datafile '/u01/app/oracle/oradata/orcl/test_1.dbf' offline
*
ERROR at line 1:
ORA-01145: offline immediate disallowed unless media recovery enabled