The IBM 360 had a scheme of locking 2-KB blocks by assigning each one a 4-bit key and having the CPU 1 answer below »

The IBM 360 had a scheme of locking 2-KB blocks by assigning each one a 4-bit key and having the CPU compare the key on every memory reference to the 4-bit key in the PSW. Name two drawbacks of this scheme not mentioned in the text.