Two processes, $A$ and $B,$ each need three records, $1, 2,$ and $3,$ in a database. If $A$ asks for them in the order $1, 2, 3,$ and $B$ asks for them in the same order, deadlock is not possible. However, if $B$ asks for them in the order $3, 2, 1,$ then deadlock is possible. With three resources, there are $3!$ or six possible combinations in which each process can request them. What fraction of all the combinations is guaranteed to be deadlock free?