sysdba VS sysasm in 11gR2

[11gr2@rh5 ~]$ sqlplus '/ as sysdba'

SQL*Plus: Release 11.2.0.2.0 Production on Sun Nov 7 20:35:17 2010

Copyright (c) 1982, 2010, Oracle.  All rights reserved.


Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - Production
With the Automatic Storage Management option

SQL>  alter diskgroup DATA rebalance power 0;
 alter diskgroup DATA rebalance power 0
*
ERROR at line 1:
ORA-15032: not all alterations performed
ORA-15260: permission denied on ASM disk group


SQL> alter diskgroup data add disk '/dev/hda10';
alter diskgroup data add disk '/dev/hda10'
*
ERROR at line 1:
ORA-15032: not all alterations performed
ORA-15260: permission denied on ASM disk group


SQL> exit
Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - Production
With the Automatic Storage Management option
[11gr2@rh5 ~]$ sqlplus '/ as sysasm'

SQL*Plus: Release 11.2.0.2.0 Production on Sun Nov 7 20:35:35 2010

Copyright (c) 1982, 2010, Oracle.  All rights reserved.


Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - Production
With the Automatic Storage Management option

SQL> alter diskgroup DATA rebalance power 0;

Diskgroup altered.

SQL>
SQL> alter diskgroup data add disk '/dev/hda10';

Diskgroup altered.