Device for setting keys without shutdown

An unlock key setting apparatus is provided which makes it possible to perform a change of memory keys without shutdown operations of other processors of a multiprocessor system. With this device, a memory key accessible to a plurality of processors of the multiprocessor system is updated without shutting down operations of the plurality of processors. Since the memory key is updated without decommissioning from other operations, the memory key can be determined by a processor as a memory key having a value at the beginning of an operation performed by the processor and a second value at the end of the operation. A mechanism is provided to allow the operation to continue, thereby avoiding a fatal exception.