In a database management system (DBMS), transactions have several properties that ensure the integrity and consistency of the database. These properties, known as the ACID properties, are:
- Atomicity: This property ensures that a transaction is an atomic unit, which means that it is either completed in its entirety or not completed at all. If an error occurs during a transaction, all the changes made during the transaction are rolled back, and the database is returned to its previous state.
- Consistency: This property ensures that a transaction must leave the database in a consistent state. For example, if a transaction is transferring money from one bank account to another, it must ensure that the sum total of all accounts remains unchanged.
- Isolation: This property ensures that the changes made by one transaction are isolated from the changes made by other transactions. This is important because it prevents transactions from interfering with each other and ensures that each transaction is processed as if it were the only transaction being processed.
- Durability: This property ensures that once a transaction has been committed, the changes made by the transaction are permanent and cannot be lost due to a system failure.
These properties help ensure the integrity and consistency of the database, and are essential to the functioning of any DBMS.