Explanation
REQ1
Once P0 is allocated with (0,0,2), the status of the system will be as follows
With available (3, 2, 0) only P1 can be served. Once P1 is executed, available will be (6, 4, 0) with (6, 4, 0) we can’t serve either P0 or P2. Hence there is no safe sequence. Hence REQ1 can’t be permitted.
REQ2
Once P1 is allocated with (2, 0, 0), the status of the system will be as follows
With available (1, 2, 2), we can serve either P1 or P2.
If we serve P1 then the safe sequence is (P1, P2, P0). If we serve P2 then the safe sequence is (P2, P1, P0). As true is at least one safe sequence we can permit REQ2.