1. A method of data processing in a data processing system, said method comprising: in response to execution of program code, initializing a control register within scrubbing logic in a local coherency domain with at least a target address of a target memory block; in response to said initializing, said scrubbing logic issuing to at least one cache hierarchy in a remote coherency domain a domain indication scrubbing request targeting a target memory block that may be cached by said at least one cache hierarchy; and in response to receipt of a coherency response indicating that said target memory block is not cached in said remote coherency domain, updating a domain indication in said local coherency domain to indicate that said target memory block is cached, if at all, only within said local coherency domain.