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Travka [436]
2 years ago
15

E xercise 17.2.4: The following is a sequence of undo-log records written by two transactions T and U: < START T>; ; <

START U>; ; ; ; ; < T ,E , 50>; . Describe the action of the recovery manager, including changes to both disk and the log, if there is a crash and the last log record to appear on disk is: (a) < START U> (b) (c) < T ,E , 50> (d) .
Computers and Technology
1 answer:
masya89 [10]2 years ago
7 0

Answer:

Check the explanation

Explanation:

The following is a sequence of Undo — log records written by two transactions.

<START 1>; <F, A, 10>; <START U>; <U, B, 20>; <F, C, 30>; <U, D, 40>; <COMMIT U>; <T, E, 50>; <COMMIT T>; (a) < START U >;

If the system crashes after the log < START U >,

Then we have log records will be shown below.

<START U>;

<T, A, 10>;

<START T>;

SYSTEM CRASHED

The recovery manager sees the Undo - Redo log and inspect the both trans-actions T and U are not committed. Then those elements changed by both transactions are arranged to their old values.

  1. Transaction T changes the element A.
  2. Then the Element A is arranged to old value A=10.
  3. Transaction U did not change any existing element in the records.
  4. So, not anything to do with transaction U.

(B) < T, E, 50>;

If the system crashes after the log < T, E, 50>;

Then we have log records will be shown below .

START T>;

<T, A, 10>;

<START U>;

<U, B, 20>;

<T, C, 30>;

<U, D, 40>;

<COMMIT U>;

<T, E, 50>;

SYSTEM CRASHED

The recovery manager sees the Redo logs and inspect the transaction U is committed or not. Such changes made by transaction U are reached to disk.

• So much the recovery manager arranged the elements to their recent values changed by transaction U.

• Transaction U changed the elements B and its records <U, B, 20>with re-cent values.

• Transaction U changed the elements D and its records <U, D, 40>with recent values.

• The transaction T is not committed.

• Then the elements changed by transaction T are arranged to old values.

• Then element A is arranged to 10, C is arranged to 30 and E is arranged to 50.

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My name is Ann [436]

Equality and Relational Operators

For the statement to return false, you can simply use the "not equal to" equality operation. The full symbol of this operation is '!=', disregarding the quotes.

<u>Examples:</u>

  • [1 != 1]  would produce FALSE. Translation: 1 <u>does not equal</u> 1?
  • [1 == 1]  would produce TRUE. Translation: 1 <u>does</u> 1?
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CONCLUSION: Use "!=".

8 0
2 years ago
Write a method printShampooInstructions(), with int parameter numCycles, and void return type. If numCycles is less than 1, prin
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Answer:

import java.util.Scanner;

public class nu3 {

   public static void main(String[] args) {

       Scanner in = new Scanner(System.in);

       System.out.println("Enter number of cycles");

       int numCycles = in.nextInt();

       //Call the method

       printShampooInstructions(numCycles);

   }

   public static void printShampooInstructions(int numCycles){

                if (numCycles<1){

              System.out.println("Too few");

          }

          if (numCycles>4){

              System.out.println("Too Many");

          }

          else {

              for (int i = 1;i <= numCycles; i++) {

                  System.out.println( numCycles+ ": Lather and rinse");

                  numCycles--;

              }

              System.out.println("     Done");

          }

   }

}

Explanation:

This is solved using Java programming language

The method printShampooInstructions() is in bold in the answer section

I have also provided a complete program that request user to enter value for number of cycles, calls the method and passes that value to it

The logic here is using if .... else statements to handle the different possible values of Number of cycles.

In the Else Section a loop is used to decrementally print the number of cycles

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Answer:

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Explanation:

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This program will store roster and rating information for a soccer team. Coaches rate players during tryouts to ensure a balance
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Answer:

Question Options :

(1) Prompt the user to input five pairs of numbers: A player’s jersey number (0 – 99) and the player’s rating (1 – 9). Store the jersey numbers in one int array and the ratings in another int array. Output these array(i.e., output the roster).

(2) Implement a menu of options for a user to modify the roster. Each option is represented by a single character. The program initially outputs the menu, and outputs the menu after a user chooses an option. The program ends when the user chooses the option to Quit. For this step, the other options do nothing. (2 pt)

(3) Implement the “Output roster” menu option. (1 pt)

(4) Implement the “Add player” menu option. Prompt the user for a new player’s jersey number and rating. Append the values to the two arrays. (1 pt)

(5) Implement the “Delete player” menu option. Prompt the user for a player’s jersey number. Remove the player from the roster (delete the jersey number and rating). (2 pts)

(6) Implement the “Update player rating” menu option. Prompt the user for a player’s jersey number. Prompt again for a new rating for the player, and then change that player’s rating. (1 pt)

(7) Implement the “Output players above a rating” menu option. Prompt the user for a rating. Print the jersey number and rating for all players with ratings above the entered value. (2 pts)

/******************************************************************************

This program will store roster and rating information for a soccer team.

                             

*******************************************************************************/

#include <iostream>

#include <vector>

using namespace std;

int main() {

   vector< int> jerseyNumber;

   vector< int> rating;

   int temp;

   for (int i = 1; i <= 5; i++) {

       cout << "\nEnter player " << i << "'s jersey number: ";

       cin >> temp;

       if ((temp >= 0) && (temp <= 99)){

           jerseyNumber.push_back(temp);}

       cout << "Enter player " << i << "'s rating: ";

       cin >> temp;

       if ((temp >= 0) && (temp <= 9)){

       rating.push_back(temp);}

       cout << endl;

   } cout << endl;

   cout << "ROSTER" << endl;

   for (int i = 0; i < 5; i++)

cout << "Player " << i + 1 << " -- " << "Jersey number: " << jerseyNumber.at(i) << ", Rating: " << rating.at(i) << endl;

   char option;

   while (true) {

       cout << endl;

       cout << "MENU" << endl;

       cout << "a - Add player" << endl;

       cout << "d - Remove player" << endl;

       cout << "u - Update player rating" << endl;

       cout << "r - Output players above a rating" << endl;

       cout << "o - Output roster" << endl;

       cout << "q - Quit" << endl << endl;

       cout << "Choose an option: " << endl;

       cin >> option;

       switch (option) {

           case 'a':

           case 'A':

               cout << "Enter another player's jersey number: " << endl;

               cin >> temp;

               if ((temp >= 0) && (temp <= 99)){

                   jerseyNumber.push_back(temp);}

               cout << "Enter another player's rating: " << endl;

               cin >> temp;

               if ((temp >= 0) && (temp <= 9)){

                   rating.push_back(temp);}

               break;

           case 'd':

           case 'D':

               cout << "Enter a jersey number: ";

               cin >> temp;

               for (int i = 0; i < jerseyNumber.size(); i++) {

                   if (jerseyNumber.at(i) == temp) {

                       jerseyNumber.erase(jerseyNumber.begin() + i);

                       rating.erase(rating.begin() + i);

                       break; }

               } break;

           case 'u':

           case 'U':

               cout << "Enter a jersey number: ";

               cin >> temp;

               for (int i = 0; i < jerseyNumber.size(); i++) {

                   if (jerseyNumber.at(i) == temp) {

                       cout << "Enter a new rating " << "for player: ";

                       cin >> temp;

                       rating.at(i) = temp;

                       break; }

               } break;

           case 'r':

           case 'R':

               cout << "Enter a rating: ";

               cin >> temp;

               cout << "\nABOVE " << temp << endl;

               for (int i = 0; i < jerseyNumber.size(); i++)

                   if (rating.at(i) > temp)

               cout << "Player " << i + 1 << " -- " << "Jersey number: " << jerseyNumber.at(i)

               << ", Rating: " << rating.at(i) << endl;

               break;

           case 'o':

           case 'O':

               cout << "ROSTER" << endl;

               for (int i = 0; i < jerseyNumber.size(); i++)

               cout << "Player " << i + 1 << " -- " << "Jersey number: " << jerseyNumber.at(i)

               << ", Rating: " << rating.at(i) << endl;

               break;

           case 'q':

               return 0;

               default: cout << "Invalid menu option." << " Try again." << endl;

       }

     }

   }

Explanation:

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