What makes a sequence of database operations a transaction
The correct answer and explanation is:
Correct Answer:
A sequence of database operations becomes a transaction when it satisfies the ACID properties: Atomicity, Consistency, Isolation, and Durability.
Explanation:
A transaction in a database context is a logical unit of work that contains one or more operations (such as insert, update, delete, or read). To be considered a valid transaction, the operations must be executed in a way that preserves the integrity of the database. This is ensured through the ACID properties:
- Atomicity: This means that a transaction is treated as a single, indivisible unit. Either all the operations in the transaction are completed successfully, or none are. If any part fails, the entire transaction fails, and the database remains unchanged. This prevents partial updates that could lead to inconsistent data.
- Consistency: A transaction must transition the database from one valid state to another. The rules, constraints, and triggers defined in the database must be followed. If the transaction violates any of these, it is rolled back. This ensures that data integrity is preserved.
- Isolation: Transactions must not interfere with each other. When multiple transactions occur at the same time, each should behave as if it is the only one running. This avoids conflicts such as reading uncommitted data from other transactions or overwriting changes.
- Durability: Once a transaction is committed, its changes are permanent, even if the system crashes right after. This is ensured through mechanisms like transaction logs and backups.
Together, these properties ensure that transactions are safe, reliable, and predictable. They play a crucial role in maintaining the accuracy, reliability, and consistency of the database system, especially in multi-user environments where many operations may occur at once.