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Using the 2019 data column in Table 2, what is the raw data for the following Z score: Z = -0.5  Round to two decimal places.

Suppose there are two transactions T1 and T2. T1 is to deposit 100 dollars to account A. T2 is to withdraw 50 dollars from account A. It is possible that a schedule for executing T1 and T2 concurrently has the phantom problem. 

The following transaction follows 2PL protocol. T: LockX(A), LockS(C), W(A), LockX(B), W(B), Unlock (A), Unlock(B), R(C), Unlock(C) Note: A, B, C are data items. LockX() is to request for an exclusive lock. LockS() is to request for a share lock. Unlock() is to release a lock. 

If a system uses strict 2PL, it can prevent from having any phantom read issue.

The following schedule is serializable. R1(A), W1(A), R2(C), W2(C), R2(B), W2(B), R1(C), R1(B), W1(B)  Note: R, W refer to Read and Write operations. A, B, C refer to the data items. 1, 2 refer to the transaction id. For example, R1(A) means Transaction 1 reads A. 

The following schedule is unrecoverable: R1(A), R1(B), R2(A), W2(B), Commit_2, W1(B), Abort_1.                          Note: R, W refer to Read and Write operations. A, B, C refer to the data items. 1, 2 refer to the transaction id. For example, R1(A) means Transaction 1 reads A.  Commit_2 means Transaction 2 commits.  Abort_1 means Transaction 1 aborts. 

Which of the following is a contradictory sentence (a sentence that can never be true)?

What have you proven when you derive both Ψ and ¬Ψ in an indirect proof?

Complete this short indirect proof. Fill in the missing line. (P → Q) Premise ¬Q Premise |_P AIP (Assumption for Indirect Proof) |_[BLANK-1]  Modus Ponens [BLANK-2], [BLANK-3] ¬P 4,2, Contradiction, IP What should line 4 be?

Cell phones should be silenced when watching a theater performance.