What: When dropping an online disk from a diskgroup why is ORA-15067 error returned?
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.
Resolution: 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.