/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 15 Describe the shadow paging recov... [FREE SOLUTION] | 91影视

91影视

Log out

Learning Materials

Features

Discover

Chapter 19: Problem 15

Describe the shadow paging recovery technique. Under what circumstances does it not require a log?

Short Answer

Expert verified
Shadow paging is a recovery technique in databases where changes during a transaction are made in a memory-based shadow page, with the current page being replaced only after a successful transaction, and the shadow page discarded after an unsuccessful one. Under normal circumstances, shadow paging doesn't require a log since the atomicity and durability properties of transactions are preserved by just discarding shadow pages in the event of a crash. However, when managing concurrent transactions, a log is often used to record the order of transactions to prevent conflicts and ensure consistency.

Step by step solution

01

Understand Shadow Paging

Shadow Paging is a technique used in database systems for achieving atomicity and durability of transactions. During the transaction, changes are made in a separate area in memory, creating a shadow page. The original page, or current page, stays unchanged. Once the transaction is completed successfully, the shadow page replaces the current page. If the transaction is not successful, the shadow page is simply discarded.
02

Shadow Paging and Logs

In Shadow Paging, logs might not be always necessary. This is because the recovery system can achieve atomicity and durability properties of transactions without needing to keep a log. In the event of a system crash, the database can recover by simply discarding the shadow pages and retaining the original pages. Thus, there is no need to rollback any transactions recorded in a log.
03

Note the Exceptions

However, there are certain exceptions. For instance, when the database system operates concurrently with several transactions, logging may be necessary to record the order of transactions. This log helps in preventing conflicts, ensuring consistency when two or more transactions are trying to access the same data element. Hence, while shadow paging doesn't necessarily demand a log, it is often employed for managing concurrent transactions more efficiently.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91影视!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

How can recovery handle transaction operations that do not affect the database, such as the printing of reports by a transaction?

What do the terms steal/no-steal and force/no-force mean with regard to buffer management for transaction processing.

Choose the correct answer for each of the following multiple-choice questions: The write ahead logging (WAL) protocol simply means that a. the writing of a data item should be done ahead of any logging operation. b. the log record for an operation should be written before the actual data is written. c. all log records should be written before a new transaction begins execution. d. the log never needs to be written to disk.

Choose the correct answer for each of the following multiple-choice questions:Incremental logging with deferred updates implies that the recovery system must necessarily a. store the old value of the updated item in the log. b. store the new value of the updated item in the log. c. store both the old and new value of the updated item in the log. d. store only the Begin Transaction and Commit Transaction records in the log.

What are the before image (BFIM) and after image (AFIM) of a data item? What is the difference between in-place updating and shadowing, with respect to their handling of BFIM and AFIM?
See all solutions

Recommended explanations on Computer Science Textbooks

Databases

Read Explanation

Computer Systems

Read Explanation

Problem Solving Techniques

Read Explanation

Data Structures

Read Explanation

Computer Network

Read Explanation

Blockchain Technology

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.