Conflict serializibility So, the task is to prove the following:


  If S is a schedule containing at most one write action, then S is conflict-serializable.


The answer is yes, but I disagree, because the following schedule contains at most one write action, and is not conflict-serializable:


  R1(A), R2(A), W2(A), R1(A).


Am I completely wrong? Or is the answer wrong?
The resulting precedence graph for your example will contain a cycle due to $R1(A) W2(A) R1(A)$. Hence its not conflict serializable. Since one example is sufficient to disprove the statement, therefore I agree with you. The answer might be wrong.