A Level Computer Science OCR Practice Exam

In database transactions, what is meant by isolation?

1. Ensuring transactions are executed in order

2. Preventing transactions from interfering with each other

3. Guaranteeing data consistency

4. Recording all transaction details

The correct answer is: Preventing transactions from interfering with each other

Isolation in database transactions refers to the property that ensures that transactions are executed independently from one another. This means that the operations involved in one transaction do not affect the operations and data of another ongoing transaction. When multiple transactions are executed simultaneously, isolation guarantees that they do not interfere with each other, thus preserving the integrity of the data. For instance, if one transaction is updating data while another transaction is reading from the same data set, isolation ensures that the read transaction will see a consistent snapshot of the data, unaffected by the updates from the first transaction until it is completed. This is crucial in concurrent environments to avoid issues such as dirty reads, non-repeatable reads, or phantom reads, which can lead to data anomalies and corruption. The other choices, while related to transaction management in databases, do not specifically define isolation. Executing transactions in order pertains to the serializability aspect, guaranteeing data consistency relates to the property of consistency in ACID (Atomicity, Consistency, Isolation, Durability) principles, and recording all transaction details involves logging rather than isolation. Thus, the concept of isolation is primarily about preventing interference between concurrent transactions.