ACID Properties in Databases

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What happens during a dirty read?

A transaction reads a value that has been permanently removed from the database.

A transaction updates a value before the previous read is completed.

A transaction reads a value from another transaction that has not yet been committed. (correct)

A transaction reads a committed value from another transaction.

Which of the following is NOT considered an anomaly?

Transactional isolation (correct)

Lost updates

Dirty reads

Phantom reads

What is the primary focus when studying anomalies in transactions?

How to resolve each anomaly effectively.

Understanding how to implement isolation levels.

Identifying the types of anomalies that exist.

Determining what problems arise from anomalies. (correct)

Which anomaly involves reading a value that may change before the transaction completes?

Dirty reads Signup and view all the answers

Which scenario can result in a dirty read anomaly?

A transaction reading a value that another transaction is currently modifying. Signup and view all the answers

What consequence arises from violating the consistency constraint in friendship lists?

Friend A's list may not include Friend B. Signup and view all the answers

What situation exemplifies the concept of Write Skew?

Alice and Bob alter different sets of data simultaneously. Signup and view all the answers

What might Alice observe after transferring $100 from her Account 2 to Account 1?

A loss of $100 from her total balance. Signup and view all the answers

Why is the scenario where two doctors go off call at the same time problematic?

There are no staff available to cover shifts. Signup and view all the answers

Which of the following best describes the potential issue when reading account balances at different times?

Account balances appear inconsistent at times. Signup and view all the answers

What does the isolation property in ACID ensure?

The end result of transactions appears as if they were executed one at a time. Signup and view all the answers

What type of anomalies can arise in concurrent transactions?

Anomalies can arise due to different interleaving of transaction operations. Signup and view all the answers

In Scenario 1, what is the final balance of account B after both transactions are executed?

$320 Signup and view all the answers

Which statement about transaction dependency is true?

Dependent transactions can cause unexpected behavior in the system. Signup and view all the answers

When transaction T executes before transaction U, what is the impact on account A?

Account A's balance decreases to $160. Signup and view all the answers

Which scenario represents the risk of issues arising from concurrency in distributed systems?

Concurrent transactions that modify shared resources can conflict. Signup and view all the answers

What is a consequence of poor concurrency control in distributed systems?

Increase in transaction anomalies and inconsistent results. Signup and view all the answers

What happens if transaction U executes before transaction T in the given scenarios?

Account B will have a higher balance compared to Scenario 1. Signup and view all the answers

What is a dirty read?

Reading a value that is being modified by a transaction that has not yet committed. Signup and view all the answers

What occurs during a dirty write?

A transaction overwrites an uncommitted value from another transaction. Signup and view all the answers

How can isolation help in a database transaction process?

By ensuring only committed transactions are visible to others. Signup and view all the answers

What is the final value of x if Transaction A executes before Transaction B and both transactions are committed?

2 Signup and view all the answers

What can happen if a write from one transaction overwrites a value written by another uncommitted transaction?

The system may experience data anomalies and inconsistencies. Signup and view all the answers

Which execution order will lead to a consistent database state?

Transaction A fully executes, followed by Transaction B. Signup and view all the answers

What happens to the final values of x and y if both Transaction A and Transaction B write different values but do not commit properly?

They both retain their initial values. Signup and view all the answers

Which statement correctly describes serial execution of transactions?

Only one transaction is allowed to run at a time, preventing any dirty reads or writes. Signup and view all the answers

What occurs when a transaction reads data and another concurrent transaction modifies data affecting that read before the first transaction is completed?

Phantom Read Signup and view all the answers

In the context of transactions, what is a Fuzzy Read commonly referred to as?

Dirty Read Signup and view all the answers

Which of the following scenarios best describes a Phantom Read?

A transaction reads a list of products, and another transaction adds a product during the read. Signup and view all the answers

What happens in a scenario where Transaction A modifies a value but does not commit, and Transaction B reads that value?

Transaction B will see the uncommitted value, leading to potential inconsistency. Signup and view all the answers

Which term is used to describe a read that results in inconsistent data because it retrieves a value that has been altered but not committed?

Fuzzy Read Signup and view all the answers

During which type of read might a transaction see different values for the same data item if it is retrieved multiple times?

Fuzzy Read Signup and view all the answers

Which of the following best illustrates a scenario that does NOT involve phantom reads?

A transaction reads a set of data, and another transaction deletes an unrelated record. Signup and view all the answers

What is the primary consequence of a Phantom Read during a transaction?

Transactions may act on incorrect or inconsistent data sets. Signup and view all the answers

Study Notes

ACID Properties

Isolation (I): Ensures concurrent transactions behave as if they execute one at a time, preventing interference and anomalies.
Concurrency in distributed systems can lead to unexpected behavior and anomalies.
Multiple transactions can modify shared data, resulting in different outcomes depending on the order of operations.

Anomalies

Dirty Read: A transaction reads data written by another transaction that has not yet committed, potentially seeing invalid data.
Dirty Write: A transaction overwrites data written by another uncommitted transaction, potentially causing inconsistencies.
Read Skew: Two transactions read consistent data but subsequent writes by both transactions violate a consistency constraint.
Write Skew: Two transactions read the same data but modify disjoint data sets, potentially violating a consistency constraint.
Phanton Reads: A transaction reads a set of data based on certain conditions, and another transaction modifies the data to invalidate the condition, causing inconsistency.
Fuzzy Read (Un-Repeatable Read): A transaction reads a value twice, and the value changes between reads due to an uncommitted write by another transaction.

Why We Need Concurrency?

Different isolation levels allow for different levels of concurrency and tradeoffs in terms of anomalies.
Applications can choose the appropriate isolation level based on their specific needs.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz explores the crucial ACID properties in database transactions, focusing on isolation and its importance in preventing anomalies. It delves into common database anomalies such as dirty reads, dirty writes, and phantom reads, alongside their implications in concurrency. Assess your understanding of these essential concepts in database management.