Concurrent Transaction Processing

In addition to Browser displayProgramIt belongs to the category of "online processing. Generally, "online processing" can be divided into "online transaction processing" (OLTP, online transaction process) and "Online Analytical Processing" (OLAP, online analytics process. The concept of transaction comes from the database. In the database, transaction is a program execution unit that accesses and may update various data items in the database ).

With the development of technology, transactions are not limited to the database field. At this stage, we generally use two perspectives to describe a transaction. One is from an external perspective, and the transaction is the basic unit of recovery and concurrency control. Another advantage is the internal point of view: a transaction is composed of a series of actions that are inseparable and cannot be wrong. Although the perspective of transactions continues to be presented with the development of technology, the attributes used to describe and evaluate transactions remain unchanged. A transaction should have four attributes: atomicity, consistency, isolation, and durability. These four attributes are generally called ACID properties.

• atomicity (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.