Which of the following transaction isolation levels allows dirty reads?

The correct answer is D. Read uncommitted. Read Uncommitted (D) is the only isolation level that permits dirty reads - it allows a transaction to see changes made by other transactions that haven't been committed yet, meaning you could read data that gets rolled back and never actually existed. The distractors are wrong b

Database Fundamentals

Question

Options

ASnapshot
BRepeatable read
CSerializable
DRead uncommitted
ERead committed

How the community answered

(52 responses)

A
6% (3)
B
4% (2)
C
2% (1)
D
88% (46)

Explanation

Read Uncommitted (D) is the only isolation level that permits dirty reads - it allows a transaction to see changes made by other transactions that haven't been committed yet, meaning you could read data that gets rolled back and never actually existed.

The distractors are wrong because each represents a stricter level of isolation: Read Committed (E) prevents dirty reads by only showing committed data; Repeatable Read (B) additionally prevents non-repeatable reads; Serializable (C) is the strictest level, preventing phantom reads as well; and Snapshot (A) uses versioning to give each transaction a consistent point-in-time view of data, inherently avoiding dirty reads.

Memory tip: Think of isolation levels as a ladder of protection - Read Uncommitted sits at the very bottom with no protection against dirty reads. The name itself is the clue: you're reading data that is still "uncommitted," i.e., potentially dirty.

Topics

#Transaction Isolation Levels#Dirty Reads#Read Uncommitted#ACID Properties

Community Discussion

No community discussion yet for this question.

Full DS0-001 Practice