A Level Computer Science OCR Practice Exam

Which property ensures that a transaction must either complete fully or fail as a whole?

1. Consistency

2. Atomicity

3. Isolation

4. Durability

The correct answer is: Atomicity

Atomicity is the property that guarantees a transaction in a database management system must either be completed fully or not executed at all. This concept is fundamental to ensuring the integrity of the database when multiple transactions are occurring simultaneously. When a transaction is executed, atomicity ensures that all operations within that transaction are treated as a single unit. If any part of the transaction fails due to an error or any other reason, the entire transaction is rolled back, meaning that any changes made during that transaction are not saved to the database. This all-or-nothing approach prevents the database from entering an inconsistent state, where some changes from a transaction are applied while others are not. Other properties like consistency, isolation, and durability contribute to the overall reliability and integrity of transactions, but they address different aspects of transaction management. Consistency ensures that a transaction brings the database from one valid state to another. Isolation ensures that transactions do not interfere with each other, thereby maintaining the accuracy of data during concurrent operations. Durability guarantees that once a transaction has been committed, it will survive system failures and will not be lost. While all these properties work together to maintain database integrity, it is atomicity that specifically focuses on the requirement that a transaction must complete in its entirety or