1. A computer implemented method for deactivating an active operand, the active operand being an instruction accessible architecturally defined operand, wherein access to a deactivated operand need not return values previously stored to the operand, the method comprising: executing, by a processor, an operand deactivating (OD) instruction, the OD instruction comprising an opcode field having an opcode value, the OD instruction having an associated operand to be deactivated, the execution comprising: determining a last-use of the associated operand; performing an opcode defined function using the associated operand; and placing the associated operand in a deactivated state.