In many cases, without delivery confirmation, the sender knows that something was sent, but there is no confirmation ___ whether was received or when it was received.

Immediately after adding a new disk to or removing an existing disk from an ASM instance, you find that the performance of the database goes down initially until the time the addition or removal process is completed, and then gradually becomes normal.
Which two activities would you perform to maintain a consistent performance of the database while adding or removing disks?（）