A data processing system having a processor and a target device processes decorated instructions (i.e. an instruction having a decoration value). A device of the data processing system such as the processor sends transactions to the target device over a system interconnect. A decorated storage notify (DSN) transaction includes an indication of an instruction operation, an address associated with the instruction operation, and a decoration value (i.e. a command to the target device to perform a function in addition to a store or a load). The transaction on the system interconnect includes an address phase and no data phase, thereby improving system bandwidth. In one form the target device (e.g. a memory with functionality in addition to storage functionality) performs a read-modify-write operation using information at a storage location of the target device.