One of the possibilities within ASM that is not widely documented is the opportunity to add disks, drop disks and set the rebalance power all in one command.
One might wonder when you might be both adding and dropping disks simultaneously from the same disk group. Recently we have been migrating to a new storage array and this command comes in very useful in that situation
alter diskgroup data add disk '/dev/oracle/disk100','dev/oracle/disk101','dev/oracle/disk102' drop disk '/dev/oracle/disk197','dev/oracle/disk198','dev/oracle/disk199' rebalance power 5;
