Transaction: A Program Execution Unit that accesses and may update various data items in the database. It is the basic unit of recovery and concurrency control. Atomicity, consistency, isolation, and durability.
- Atomicity ). A transaction is an inseparable unit of work. All operations involved in a transaction are either done or not done.
- Consistency ). Transactions must change the database from one consistent state to another. Consistency is closely related to atomicity.
- Isolation ). The execution of a transaction cannot be disturbed by other transactions. That is to say, the operations and data used within a transaction are isolated from other concurrent transactions, and the transactions executed concurrently cannot interfere with each other.
- Durability ). Permanence refers to a transaction that changes the data in the database once committed. Other subsequent operations or faults should not have any impact on them.
