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Chapter 19: Problem 13

Discuss the immediate update recovery technique in both single-user and multi user environments. What are the advantages and disadvantages of immediate update?

Short Answer

Expert verified
The Immediate Update Recovery Technique is a database recovery mechanism wherein updates are immediately recorded in the database, irrespective of the transaction's commit status. While this improves concurrency and speeds up execution, it may lead to data inconsistencies, especially in multi-user environments where transactions can interfere with each other. Here, it requires a rollback mechanism whose complexity can be viewed as a disadvantage.

Step by step solution

01

Definition of Immediate Update Recovery Technique

The Immediate Update Recovery Technique, also known as the Eager Update technique, is a database recovery mechanism. As soon as the transaction results become available, they are updated in the database, irrespective of the transaction's commit status.
02

Application in Single-User Environment

In a single-user environment, immediate update technique works smoothly as there is only one transaction active at a time. When a transaction makes changes, such changes are immediately recorded in the database.
03

Application in Multi-User Environment

However, in a multi-user environment, transactions can interfere with each other while using immediate update technique. If a transaction fails after having made changes to the database, other transactions may have already viewed and potentially used those changes, leading to inconsistencies. Hence, in such cases, a rollback mechanism is required to ensure data integrity.
04

Advantages of Immediate Update

Immediate Update method improves the concurrency in the system since the changes made in the buffer can immediately be used by other transactions. It also leads to faster execution as there is no need to wait until the end to commit changes.
05

Disadvantages of Immediate Update

The immediate update method poses a great risk of data inconsistency and requires a rollback mechanism. A transaction might make changes to the database that've been utilized by other transactions before it has had a chance to commit or rollback. Upon transaction failure, not only the actual transaction needs to be rolled back, but, potentially, the other transactions that used its uncommitted data too. This adds complexity to the system architecture.

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Most popular questions from this chapter

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?

Choose the correct answer for each of the following multiple-choice questions: To cope with media (disk) failures, it is necessary a. for the DBMS to only execute transactions in a single user environment. b. to keep a redundant copy of the database. c. to never abort a transaction. d. all of the above.

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

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.

Discuss the different types of transaction failures. What is meant by catastrophic failure?
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