n A protocol to prevent circular wait: u define a strictly increasing linear ordering O() for resource types. Ex: F R1: tape drives: O(R1) = 2 F R2: disk drives: O(R2) = 4 F R3: printers: O(R3) = 7 u A process initially request a number of instances of a resource type, say Ri. A single request must be issued to obtain several instances. u After that, the process can request instances for resource type Rj if and only if O(Rj) > O(Ri)