What is ACID? Learn about 4 important properties in databases

ACID is an important term in the field of database management, describing four essential properties that a transaction system must have to ensure the accuracy and reliability of data. This article from  TipsMake  will help you better understand the concept of ACID and its properties.

What is ACID?

ACID is an acronym that stands for four basic properties: Atomicity, Consistency, Isolation, and Durability. These properties have become the standard for ensuring that transactions in a database are safe and efficient.

What is ACID? Learn about 4 important properties in databases Picture 1

What is ACID?

When a transaction is executed, it must not only complete correctly, but also not affect the state of the system without permission. Each property in ACID plays an important role in data management, ensuring that no matter what errors occur during processing, the data remains correct and valid.

4 Properties of ACID in Databases

Let's dive into each property of ACID to better understand their meaning and practical applications.

Atomicity

Atomicity is the first property of ACID, which states that a transaction must either be committed completely or not at all.

A simple example of atomicity is when you transfer money from one bank account to another. This transaction might involve two steps: deducting money from the source account and adding money to the destination account. If the first step succeeds but the second fails, money should not be deducted from the source account because this would create data inconsistencies.

Consistency

Consistency is the second property of ACID and it deals with ensuring that a transaction takes the system from one valid state to another valid state. 

An example of consistency: When a database system has a rule that an account balance can never be negative. If a transaction attempts to perform a transaction that violates this rule, the system will reject the transaction and ensure that the data remains consistent.

To achieve consistency, it is important to regularly check and verify data. Rules can include constraints on primary keys, foreign keys, and other checks. Consistency helps ensure that data always reflects reality and that there are no inconsistencies between information in the database.

Isolation

Consistency refers to the ability of a system to process multiple transactions simultaneously without affecting each other. When multiple transactions occur in parallel, isolation ensures that each transaction acts as if it were the only transaction in the system.

Without isolation, transactions can interfere with each other, leading to data inconsistencies. There are three isolation levels in database management systems: Read Uncommitted, Read Committed, and Serializable. Each of these levels has a different approach to allowing transactions to read each other's data. Depending on the specific requirements of the application, developers can choose the appropriate level to balance performance and correctness.

Durability

Consistency ensures that once a transaction has been committed, its results will persist indefinitely even if a system fails, such as a power failure or a software failure. To achieve persistence, database systems often use backup and recovery methods, as well as log changes so that a previous state can be restored if a failure occurs.

Sustainability not only helps protect data, but also builds trust with users, knowing that their information will be stored securely. 

Extended versions of ACID

Although ACID provides a solid framework for transactions in a database, with the advancement of technology and increasing business needs, several other extensions have emerged such as:

BASE

While ACID focuses on correctness and strictness, BASE focuses on scalability and flexibility of the system. BASE stands for Basically Available , Soft state and Eventually consistent .

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BASE

1. Basically Available: The system must always provide a certain level of service, even when some parts of the system are not available.
2. Soft state: Data can change over time and does not need to be synchronized immediately.
3. Eventually consistent: Data will be consistent but not immediately. The system will ensure that any changes will eventually be synchronized.

ACID + Eventual Consistency

ACID + Eventual Consistency allows data to be inconsistent for a period of time, but will eventually achieve a consistent state. However, this also means that programmers need to pay more attention to how they handle data to avoid causing unwanted conflicts.

CQRS (Command Query Responsibility Segregation)

Command Query Responsibility Segregation (CQRS) is a design pattern that separates the responsibility of executing commands and queries. With CQRS, writing data and reading data are separated, optimizing system performance and scalability.

Advantages and disadvantages of ACID properties

ACID not only has its benefits but also its limitations. Understanding these advantages and disadvantages will help you choose the right solution for your system.

Advantage

1. Accuracy: ACID ensures that every transaction is executed correctly, helping to prevent errors and discrepancies in data.
2. Consistency: Helps maintain data consistency across the system, minimizing the possibility of conflicts and errors.
3. Data protection: Ensures that data will not be lost or corrupted, even if something goes wrong.
4. Easy to Manage: With clear rules and constraints, ACID makes it easy for developers to manage and track data.

Disadvantages

However, the ACID properties also have some disadvantages to consider:

1. Performance: Due to strict requirements for correctness, ACID transactions can be slower than other models.
2. Difficult to scale: As the number of users and data increases, maintaining atomicity and isolation can become more complex, making the system difficult to scale.
3. High Cost: Maintaining ACID properties requires higher resource utilization, resulting in higher operating costs for businesses.

Conclude

ACID is an extremely important concept in the database field. Understanding the four properties of ACID helps us to better understand how transactions are processed safely and efficiently. With the development of technology, extended versions such as BASE, CQRS are also becoming a trend in meeting the increasing demands of complex systems. Therefore, choosing the right model according to the requirements of the project is very important.

Jessica Tanner

Update 03 April 2025