A handler, which performs some optimizations often needs to act based on change
of its instance's attributes. I request that there should be an efficient way
how to do that, and receive information about the change inside the mutex held
by the operation so the Handler may consistently rebuild its private data.
I don't know if the rebuild may be allowed to fail (which would require the
_post phase used in MDR to be performed after such internal update).

This request equally applies to AssociationHandlers as well.