ORA-15067: command or option incompatible with diskgroup redundancy

SQL> alter diskgroup data01 drop disk data01_01;
alter diskgroup data01 drop disk data01_01
*
ERROR at line 1:
ORA-15067: command or option incompatible with diskgroup redundancy


Cause: 

The disk is the last one in the diskgroup. A
minimum of one disk is required for a diskgroup. For more details look
in the ASM alert log.


Solution: 

Don’t try dropping the last member of
the diskgroup. If you have to drop a particular disk and it is the last
member add another disk to the diskgroup first.