BE - Database Management Systems

In DBMS, a transaction is a single logical unit of work that consists of one or more database operations such as insert, delete, update, or retrieve. A transaction ensures that the database remains in a consistent state even in the case of system failures, errors, or concurrent execution. For example, transferring money from one bank account to another involves two operations—debiting one account and crediting another—which together form one transaction.

A transaction must satisfy the ACID properties, which are:

1. Atomicity – A transaction is all-or-nothing, meaning either all operations of the transaction are executed successfully or none of them are.

2. Consistency – A transaction must transform the database from one consistent state to another consistent state, maintaining all integrity constraints.

3. Isolation – Concurrent transactions must execute independently of one another; the execution of one transaction should not interfere with another.

4. Durability – Once a transaction has been committed, its changes to the database are permanent and survive even system failures.