## Introduction

Answer the following questions from your textbook. You may submit in any format that is neat and readable. Electronic submissions (no required) are to be submitted using D2L on or before the due date.Chapter 21, page 809, exercises 21.25 and 21.26.

## Explanation

Use the following information for both questions:Let us assume a clock with linear time points 0, 1, 2, 3... and that the original read and write timestamps of all items are 0 (without loss of generality).

read_TS(X) = read_TS(Y) = read_TS(Z) = 0

write_TS(X) = write_TS(Y) = write_TS(Z) = 0

The two schedules can be written as follows in shorthand notation:

SE:

r2(Z); r2(Y); w2(Y); r3(Y); r3(Z); r1(X); w1(X); w3(Y); w3(Z); r2(X); r1(Y); w1(Y); w2(X);

1 2 3 4 5 6 7 8 9 10 11 12 13

SF:

r3(Y); r3(Z); r1(X); w1(X); w3(Y); w3(Z); r2(Z); r1(Y); w1(Y); r2(Y); w2(Y); r2(X);w2(X);

1 2 3 4 5 6 7 8 9 10 11 12 13

Assume that each operation takes one time unit, so that the numbers under the operations indicate the time when each operation occurred. Also assume that each transaction timestamp corresponds to the time of its first operations in each schedule, so the transaction timestamps are as follows (Note: These values do not change during the schedule, since they are assigned as unique identifiers to the transactions):

Schedule E Schedule F

TS(T1) = 6 TS(T1) = 3

TS(T2) = 1 TS(T2) = 7

TS(T3) = 4 TS(T3) = 1

Each question is worth 20 points for a total of 40 points.

On this assignment, as on most assignments, you must work alone. Please do not share your work with anyone else or be shared with by anyone else. Thank you for your cooperation. All answers must include proper citations if you find information from other sources. The question that is copied without citations will receive 0 points.

## No comments:

## Post a Comment