A schedule is not conflict-serializable. Is it serializable? While reading this solved quiz on concurrency control, I got stuck on exercise 2, which reads as follows:


  2) Consider the following schedule:
  
  S: r1(X), w2(X), r3(X), r1(Y), w2(Z), r3(Y), w3(Z), w1(Y)
  
  (a) (2 points) Draw the precedence graph.
  
  
  
  (b) (1 point) Is S conflict serializable?
  
  No.


After reading that S is not conflict-serializable, my question is: can we say that S is serializable? Any suggestions?

Thanks to anyone who help me.
A schedule is considered serializable if it is equivalent to a serial one. The conflict graph that appears on the answer to item (a) is proof that the schedule is not conflict-serializable, and it is also not view-serializable, because there is still a cycle between $T_1$ and $T_3$, when considering just the history of the data they visualize. That means the schedule cannot be considered serializable at all.

Conflict-serializability is stronger than view-serializability. It is the criterion used for the implementation of most schedulers, and that is why the quiz emphasizes this point.