Transaction semantics: Is a transaction a series of database actions that must all succeed together, or else none take effect (all-or-nothing)?

Introduction / Context:
Transactions provide a clean unit of work in database systems. The key property highlighted here is atomicity: a transaction’s changes are applied entirely or not at all. This property underpins reliable application behavior in the face of errors or crashes.

Given Data / Assumptions:

• A transaction encloses multiple reads and writes.
• Commit makes changes durable; rollback undoes them.
• System may crash, but recovery respects atomicity.

Concept / Approach:
ACID stands for Atomicity, Consistency, Isolation, Durability. Atomicity is the “all-or-nothing” guarantee. Consistency requires that transactions move the database from one valid state to another, Isolation controls interference among concurrent transactions, and Durability guarantees that committed changes persist.

Step-by-Step Solution:

Verification / Alternative check:
Crash recovery replays/undoes logged operations to ensure either the full transaction is applied or not applied, never a partial state.

Why Other Options Are Wrong:

• “Incorrect” contradicts the definition of atomicity.
• Transaction semantics do not apply “only for read-only” or depend solely on autocommit; even with autocommit, each statement is a transaction.

Common Pitfalls:
Mistaking batch execution for transactional grouping. Without explicit transaction control, some drivers autocommit per statement; still, each statement is atomic.

Final Answer:
Correct