These are Data Base Management System Week 8 Assignment Answers
Q1. Assume an immediate database modification scheme. Consider the following log records for transactions TO, T1, T2, T3 and T4: If there is a crash just after step 14 and the recovery of the system is successfully completed, identify the correct actions for the above scenario. a) After recovery completion, value of X will be 300. b) After recovery completion, value of Y will be 600. c) After recovery completion, value of W will be 300. d) After recovery completion, value of V will be 100.
Answer: b), c)
Q2. Identify the cost estimation of a query evaluation plan, if 1000 blocks are required to transferred from the disk and the required number of disk seeks are 30. • Time to transfer one block: tr = 4 milliseconds. • Time for one seek: ts = 0.3 seconds. a) 10 Seconds b) 13 Seconds c) 15 Seconds d) 25 Seconds
These are Data Base Management System Week 8 Assignment Answers
Q3. Assume an immediate database modification scheme. Consider the following log records for transactions T1, T2, T3 and T4: If there is a crash just after step 12 and the recovery of the system is successfully completed, identify the correct action for the above scenario. a) No Action: T2; Redo: T1, T4; Undo: T3 b) No Action: T2; Redo: T1, T3; Undo: T4 c) No Action: T1; Redo: T2, T3; Undo: T4 d) No Action: T1; Redo: T2, T4; Undo: T3
Answer: b) No Action: T2; Redo: T1, T3; Undo: T4
Q4. Let us consider the following statistics for two relations of Books and Authors: • Number of records of Books: nBooks 3000. • Number of blocks of Books: bBooks = 300. • Number of records of Authors: Authors= 1500. • Number of blocks of Authors: bAuthors= 30. Identify the required number of block transfers and seeks if the smaller relation fits entirely in memory, use that as the inner relation using Nested-loop join. a) 4830 block transfers and 2 seeks b) 4500 block transfer and 2 seeks c) 330 block transfers and 2 seeks d) 300 block transfers and 2 seeks
These are Data Base Management System Week 8 Assignment Answers
Q5. Which of the following statement(s) is (are) true? a) The log is a sequence of log records, which maintains information about update activities on the database. b) The log is a sequence of schedules, which maintains information about each schedules topological orderings. c) Physical blocks are those blocks which reside temporarily in the main memory. d) Physical blocks are those blocks residing on the disk.
These are Data Base Management System Week 8 Assignment Answers
Q6. Consider the log record of transaction To, transaction T1 with operation instance 01 used in recovery system with early lock release, B+ tree based concurrency control. Choose the correct set of log entries for the recovery of transactions.
These are Data Base Management System Week 8 Assignment Answers
Q7. Consider the following relational schema: Students (student_id, student name, address, email) Courses (course_id, course name, credits) Registrations(student_id, course_id, semester, grade) Two query trees are given below. Identify the correct statement for the above two query trees. a) Two query trees are equivalent as selection operation can be carried out before or just after performing the natural join. b) Two query trees are not equivalent as selection operation can not be carried out before performing the natural join. c) Two query trees are equivalent and the query tree of Figure 1 will lead to more efficient query processing. d) Two query trees are equivalent and the query tree of Figure 2 will lead to more efficient query processing.
These are Data Base Management System Week 8 Assignment Answers
Q8. Consider the following relational schema: Students(student id, student name, address, email) Courses (course id, course name, credits) Registrations(student_id, course id, semester, grade) Four relational algebra queries are given below: Identify the correct options from the options given below. a) Q1 is equivalent to Q2. b) Q1 is not equivalent to Q2. c) Q3 is equivalent to Q4. d) Q3 is not equivalent to Q4.
These are Data Base Management System Week 8 Assignment Answers
Q9. Consider the following state of transactions and the statements below. T1, T2 and T4 can be ignored. 2. T1, T2 and T3 can be ignored. 3. T3 and T6 needs to be redone. 4. T3, T4 and T6 needs to be redone. 5. Only T5 need to be undone. Identify the correct group of statements from the options below. a) 1), 2), 3) b) 1), 3), 5) c) 2), 4), 5) d) 2), 3), 5)
These are Data Base Management System Week 8 Assignment Answers
Q10. Consider the Relational Algebra expression given below: (PQ) (PMR) where P, Q, and R are relational algebra expressions. Identify the correct equivalent relational algebra expression of the above relational algebra expression. a) PM (QR) b) ((PQ)R) c) (PQ)-(PR) d) PM (QR)
These are Data Base Management System Week 8 Assignment Answers
Q1. Assume that immediate database modification scheme is followed in this question. Consider the following log records for transactions TO, T1, T2, T3 and T4:
If there is a crash just after step 13 and the recovery of the system is successfully completed, identify the correct action for the above scenario. a) After recovery completion, value of A will be 200. b) After recovery completion, value of C will be 800. c) After recovery completion, value of D will be 500. d) After recovery completion, value of E will be 700.
These are Data Base Management System Week 8 Assignment Answers
Q2. Assume that immediate database modification scheme is followed in this question. Consider the following log records for transactions T0, T1, T2, T3 and T4:
If there is a crash just after step 14 and the recovery of the system is successfully completed, identify the correct action for the above scenario. a) No Action: TO, T1; Redo: T3 and Undo: T2, T4 b) No Action: TO; Redo: T3 and Undo: T1, T2, T4 c) No Action: T1; Redo: T2, T3 and Undo: TO, T4 d) No Action: T1; Redo: T2, T4 and Undo: TO, T3
Answer: c) No Action: T1; Redo: T2, T3 and Undo: TO, T4
These are Data Base Management System Week 8 Assignment Answers
Q3. Identify the cost estimation of a query evaluation plan, if 6000 blocks are required to be transferred from the disk and the required number of disk seeks are 30. Time to transfer one block: ty = 2 milliseconds. Time for one seek: tg = 0.2 seconds. a) 12.2 Seconds b) 16 Seconds c) 18 Seconds d) 48 Seconds
Answer: c) 18 Seconds
These are Data Base Management System Week 8 Assignment Answers
Q4. Let us consider the following statistics for two relations Professor and Appointment Details: Number of records of Professor: nprofessor = 4000. Number of blocks of Professor: bprofessor = 50 Number of records of Appointment Details: npppointment Details = 2000. Number of blocks of Appointment Details: bppointment Details = 20 Let us consider a natural join of Professor and Appointment Details relations (Professor» Appointment Details). Identify the required number of block transfers in the worst case (enough memory only to hold one block of each relation) using Nested-loop join and assume Professor as the outer relation. a) 120050 block transfers b) 120000 block transfer c) 80050 block transfers d) 80000 block transfers
Answer: c) 80050 block transfers
These are Data Base Management System Week 8 Assignment Answers
Q5. Consider the following state of transactions and the statements below.
1. T1, T2 and T3 can be ignored. 2. T2 and T4 can be ignored. 3. T3, T4 and T5 need to be redone. 4. T4 and T5 need to be redone. 5. Only T6 needs to be undone. Identify the correct group of statements from the options below. a) 1), 2), 3), 5) b) 1), 3), 4), 5) c) 1), 4), 5) d) 2), 4), 5)
Answer: c) 1), 4), 5)
These are Data Base Management System Week 8 Assignment Answers
Q6. Consider the following relational schema: Professor(pid, pname, qualification, emaillD) Department (dname, building, budget) Appointment Details(pid, dname, date, time) Two query trees are given below.
These are Data Base Management System Week 8 Assignment Answers
Identify the correct statement for the above two query trees. a) Two query trees are equivalent as identical operations (irrespective of their positions) are used in both the trees. b) Two query trees are not equivalent as selection or projection operation cannot be carried out before or after the natural join operation. c) Two query trees are equivalent and the query tree of Figure 1 will lead to more efficient query processing. d) Two query trees are equivalent and the query tree of Figure 2 will lead to more efficient query processing.
Answer: d) Two query trees are equivalent and the query tree of Figure 2 will lead to more efficient query processing.
These are Data Base Management System Week 8 Assignment Answers
Q7. Consider the following relational schema: Professor (pid, pname, qualification, emaillD) Department (dname, building, budget) Appointment Details(pid, dname, date, time) Four relational algebra queries are given below: Q1: (9building=‘Watson’ (7date=*2021-04-15’ (Department I Appointment Details))) Q2: (pyilding, date (Department > Appointment Details)) Q3: Tpname (Professor > Appointment Details) Q4: lpname (9professor. pid=Appointment Details.pid(ProfessorxAppointment Details)) Identify the correct options from the options given below. a) Q1 is equivalent to Q2. b) Q1 is not equivalent to Q2. c) Q3 is equivalent to Q4. d) Q3 is not equivalent to Q4.
Answer: b, c
These are Data Base Management System Week 8 Assignment Answers
Q8. Consider the following relational schema: Professor (pid, pname, qualification, emaillD) Department (dname, building, budget) Appointment (pid, dname, date, time) A relational algebra expression given below: Tpname (Ipid, pname (“building=‘Packard’ (Professor i Appointment » Department))) Identify the most optimized relational algebra expression equivalent to the above given relational algebra expression. a) IIpname,pid (7building=‘Packard’ (Professor X Appointment X Department) ) b) IIpname, pid (Professor i (Appointment MX (0pyj1ding= ‘Packard’ (Department)))) c) lIpnane, pid (Professor i (Appointment X Ilgnane (7building=*Packard’ (Department)))) d) IIpname (Professor » (Appointment M (7hy;1ding=”‘Packard’ (Department))))
Answer: d) IIpname (Professor » (Appointment M (7hy;1ding=”‘Packard’ (Department))))
These are Data Base Management System Week 8 Assignment Answers
Q9. Consider the following two relational algebra expressions (RA) given below: RA I : 001 (PM02 Q) = (PM0102 Q) RA II : ((PQ) AR) = (PA (QAR)) where P, Q, and R are relational algebra expressions. Identify the correct statement(s) from the followings. a) Both RA I and RA II are true. b) Both RA I and RA II are false. c) RA I is true but RA II is false. d) RA I is false but RA II is true.
Answer: d) RA I is false but RA II is true.
These are Data Base Management System Week 8 Assignment Answers
Q10. Consider the log record of Transaction T1 with two operation instances 01 and 02 used in recovery system with early lock release, B+ tree based concurrency control.
Choose the correct set of log entries for the recovery of transactions.
These are Data Base Management System Week 8 Assignment Answers
Answer: c
These are Data Base Management System Week 8 Assignment Answers
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