11 There are two relations R1(A, B, C) and R2(B, D, E). Which of following techniques CANNOT be used to improve the performance of the natural join of the two relations?
A make use of multiple parallel processes on a multi-core machine to implement the join algorithm
B increase the CPU L2 cache hit ratio of the join algorithm implementation
C partition the relations to different machines by using join attributes and execute the join on many machines in parallel
D when the number of tuples in R2 is large and the number of tuples in R1 is small, build and index on R1 and use index join method
E none of the above
12 Which of the following statements about checkpoints(with log-based recovery schemes) in databases are/is NOT correct?
A checkpoints are used to decrease the time used for failure recovery
B checkpoints are done periodically in database to assure ACID properties of transactions
C periodic checkpoints decreased the number of log entries that need to be redone during recovery