Database Transactions

Owned by Computer Science Department
Aug 01, 2023
2 min read

A database transaction, in the context of a database management system (DBMS), is a single unit of work that is performed within a database management system or a similar system, against a database, and treated in a coherent and reliable way independent of other transactions. A transaction generally represents any change in a database.

 

Database transactions help to ensure data integrity and consistency. They follow the ACID model, which stands for Atomicity, Consistency, Isolation, and Durability.

  1. Atomicity: This property ensures that a transaction is treated as a single, indivisible unit, which either succeeds completely, or fails completely. If any part of the transaction fails, the entire transaction fails, and the database state is left unchanged.

  2. Consistency: This ensures that a transaction brings the database from one valid state to another. The database should satisfy a specific set of constraints, which define the consistency of the database.

  3. Isolation: This property ensures that the concurrent execution of transactions results in a system state that would be obtained if transactions were executed serially, i.e., one after the other. This means that for any two transactions, the result of their concurrent execution is the same as if they were executed one after the other in some order.

  4. Durability: Durability ensures that once a transaction has been committed, it will remain committed even in the case of a system failure (such as a power outage or crash). This usually means that completed transactions are recorded in non-volatile memory.

Examples of transactions include transferring money from one bank account to another, adding a record to a database, or deleting a record from a database.

Each transaction consists of one or more database operations, which could be a combination of CREATE, READ, UPDATE, and DELETE operations (also known as CRUD operations). The DBMS must ensure that these operations bundled in a transaction follow the ACID properties for data integrity and consistency.