What is defined as a single event or sequence of actions treated as a unit in database operations?

A transaction is a critical concept in database operations that refers to a single event or sequence of actions treated as a unit. This means that a transaction encompasses all the steps needed to complete a specific operation, such as inserting, updating, or deleting records in a database. The defining characteristic of a transaction is that it is designed to be atomic, meaning that all the operations within the transaction must be completed successfully for the transaction as a whole to be considered successful. If any part of the transaction fails, the entire transaction is rolled back, ensuring that the database remains in a consistent state.

Transactions are fundamental in maintaining data integrity, especially in situations where multiple users may access the database concurrently. They ensure that database operations are processed reliably and adhere to the ACID properties—Atomicity, Consistency, Isolation, and Durability—which are essential for ensuring reliable transaction processing.

The other terms like a session, query, and operation refer to different aspects of database interaction. A session might refer to the period during which a user interacts with the database, while a query is a specific request to retrieve or manipulate data. An operation could be any single action performed in a database context but does not imply the grouping and atomicity characteristic that defines a transaction.