CSI 410. Database Systems Spring 2021
作业homework | assignment | database代做 – 该题目是一个常规的database的练习题目代写, 是比较典型的database等代写方向, 该题目是值得借鉴的assignment代写的题目
The deadline for this assignment is11:59 PM, May 10, 2021.Submissions after this deadline will not be accepted. Each student is required to enter the UAlbany Blackboard system and then upload a .pdf file (in the form of [first name]_[last name].pdf) that contains answers to Problems 1-4. The total grade for this assignment is 100 points. If you find any error or have questions or suggestions, please contact the instructor ([email protected]).
Problem 1.(20 points) Determine whether or not each of the following schedules isconflict-
serializableand explain why. If conflict-serializable, show the steps of finding an equivalent serial schedule.
(a) (10 points) T 1 T 2 T 3 read(B) read(B) A := B + 10 A := B read(A) A := A + 1 write(A) write(A) write(A)
(b) (10 points) T 1 T 2 T 3 read(A) read(B) A := B + 10 B := A read(A) A := A + 1 write(A) write(A) write(B)
Problem 2.(20 points) Determine whether or not each of the following schedules isrecoverable.
Also, determine whether or not each of the following schedules iscascadeless. Justify your answer. In the schedules,ri(X)andwj(Y)representread(X)issued by transactionTiandwrite(Y)issued by transactionTj, respectively.coiindicates committing transactionTi.
(a) (10 points)r 1 (A);w 2 (A);w 1 (A);w 3 (A);r 4 (A);co 3
(b) (10 points)r 1 (A);w 2 (A);w 2 (B);r 1 (B);co 1
Problem 3.(20 points) Consider a timestamp-based concurrency control manager that assigns
timestamps to transactions in the order of their start times. In the following, stimeans that transactionTistarts andcoimeans that transactionTicommits. In each case below, explain what decision the concurrency control manager will make in response to the last read/write request.
(a) (10 points)st 1 ;st 2 ;st 3 ;w 1 (A);co 1 ;r 3 (A);w 2 (A)
(b) (10 points)st 1 ;st 2 ;st 3 ;w 1 (A);co 1 ;r 3 (B);r 2 (B)
Problem 4.(40 points) Assume a database that crashed during execution. Based on the following
log, answer each of the questions below:
(a) (10 points) What transactions were running (i.e., in theactivestate) at the time of crash?
(b) (10 points) What transactions will the system UNDO?
(c) (10 points) Show the steps of the REDO pass.
(d) (10 points) Show the steps of the UNDO pass.
After solving the above problems, please state the amount of time spent for this assignment. Feel free to add comments or suggestions if any.