In the realm of application development and database management, data integrity is paramount. The consequences of charging a customer the wrong amount or losing their data can be catastrophic for any business. Thankfully, modern SQL databases like MySQL and Postgres implement robust measures to ensure data integrity. One of the key principles underpinning this integrity is the use of transactional standards like ACID. In this blog post, we will explore the inner workings of ACID transactions and how they safeguard data integrity in databases. 

All the Challenges Faced by Transactions 

Data scientists often grapple with lengthy analytical queries and data warehousing concerns. However, for developers, databases are primarily about transactions. A database transaction refers to a series of logically grouped database operations, such as inserting a row, updating a record, or performing similar tasks. Transactions are a fundamental part of application development and are executed each time a new user signs up or updates their account information. 

Transactions, though essential, are not without their challenges. Many things can go wrong when writing to a database, including lost connections to remote instances, encountering value errors, and various other unforeseen issues.

To illustrate the potential pitfalls, consider a scenario that a company like Amazon might encounter: 

• A user updates their order quantity and clicks “order now.” 
• The system attempts to Update the order quantity in the pending orders table. 
• Add a row to the orders table. 
• Apply the purchase to the user’s balance or charge their credit card. 

If something goes awry during these operations, but the system proceeds to execute them, the user may be charged the wrong amount. Furthermore, if the charge fails, the user might receive their order for free. These types of data errors have specific names, and there are several of them.

Let’s explore a few examples: 

Dirty Reads: When a transaction is in the process of updating data but has not yet committed, and another transaction reads that uncommitted data, it is considered “dirty.” This can lead to the application displaying incorrect data that may later be rolled back. For example, imagine a transaction that invalidates login tokens when a user changes their password. If a second transaction reads the token before the first invalidates it, a dirty read occurs. 

Non-Repeatable Reads: In cases where two consecutive reads occur in one transaction with a concurrent update happening in between, the reads may yield different results, even though they are part of the same transaction. For instance, two writers collaborating on a blog may result in a non-repeatable read if one user changes the post’s title while another is reading it. 

Phantom Reads: When a transaction reads data, and a concurrent transaction inserts data that would have been part of the original transaction’s read, it is called a phantom read. This situation is similar to a non-repeatable read and can lead to data inconsistencies. 

These three types of transactional errors are defined by the SQL standard and are collectively known as the “big three.” While they may sound similar, they can overlap in practice. 

ACID Transactions: Ensuring Data Integrity 

To prevent the data integrity issues, popular relational databases like MySQL adhere to a set of core principles known as ACID. ACID is an acronym that encompasses four key properties: Atomicity, Consistency, Isolation, and Durability. These properties ensure data integrity and are essential for maintaining robust database transactions. 

Here’s a breakdown of what each component of ACID represents: 

• Atomicity: This property follows the “all or nothing” rule. A transaction is either executed completely or not at all. If something goes wrong during the transaction, it is rolled back, and no partial changes are retained. 

• Consistency: ACID transactions guarantee that data remains consistent before and after a transaction. There should be no missing or incomplete steps in the database’s state. 

• Isolation: Multiple transactions can occur concurrently without reading or writing the wrong data. Each transaction is isolated from others to prevent interference. 

• Durability: Transactional success is resilient to system failures. Once a transaction is committed, its changes are permanent and survive system crashes or other issues. 

ACID is not a specific process but a set of properties that govern how database transactions work. SQL databases achieve ACID compliance through a system called locking. Locking temporarily holds data until a transaction is completed, preventing concurrent transactions from interfering with each other. 

In a simplified analogy, think of writing in an Excel spreadsheet before saving your work. The changes you make are tentative until you either save them (commit) or discard them (abort). In the case of our Amazon example, if an error occurs after updating a user’s order quantity, the transaction will abort, and it will be as if the update never happened. If the error arises during the credit card charge, the charge will not go through. ACID transactions ensure that either everything happens correctly, or nothing happens at all. 

While the details of committing and locks can be complex, understanding the basics is a solid starting point.

ACID Concepts in NoSQL and Distributed Systems 

ACID was a foundational concept for reliable relational databases, but the advent of NoSQL databases changed the landscape. Many NoSQL databases are built as distributed systems, making it challenging to guarantee complete transactional consistency. This challenge is encapsulated by the CAP theorem, which posits that in distributed systems, it is impossible to achieve both full consistency and full availability simultaneously. A trade-off must be made. 

For NoSQL databases like MongoDB or Cassandra, a new quasi-standard called BASE (Basically Available, Soft-State, Eventually Consistent) has emerged. BASE adopts a weaker consistency model than ACID, emphasizing availability over strict consistency. Under BASE, databases are designed to work most of the time, even if they are not consistently perfect. Nodes in the database may not always be in perfect sync, but eventually, data consistency is achieved. 

In summary, while NoSQL databases have altered the landscape of data management, the foundational principles of ACID transactions continue to play a vital role. As the volume of data continues to grow, ACID’s building blocks will likely find their place in future transactional standards. For those building with databases and seeking a convenient way to add functionality, tools like Retool offer streamlined solutions. 

Current Practices for ACID Compliance in Banking 

ACID compliance is crucial in the banking industry to ensure the reliability, integrity, and security of financial data and transactions. Banks typically employ various measures to achieve and maintain ACID compliance: 

• Database Management Systems (DBMS): Banks use robust database management systems like Oracle, SQL Server, or IBM Db2 that are designed to support ACID properties. These systems offer features such as transaction logs, locking mechanisms, and data redundancy to ensure data consistency and durability. 

• Transaction Logs: Transaction logs record all changes made to the database, including transactions and updates. In case of system failures, these logs are used to restore the database to its most recent consistent state. 

• Redundancy and Replication: Banks often implement data redundancy and replication to ensure data availability and durability. This involves maintaining multiple copies of data on separate servers or data centers to minimize the risk of data loss due to hardware failures. 

• Backup and Recovery Procedures: Regular backups are taken to create copies of the database, which can be used for disaster recovery. Banks have established procedures for data backup and restoration to ensure data durability. 

• Data Encryption: To protect data during transmission and storage, banks use encryption mechanisms like SSL/TLS for secure communication and encryption at rest for data stored on servers and backup media. 

• Access Control and Authentication: Strict access controls and authentication mechanisms are in place to prevent unauthorized access to sensitive financial data. Only authorized personnel can perform transactions, and audit trails are maintained for accountability. 

• High Availability (HA) Systems: Banks invest in high availability systems that ensure continuous operation, even in the face of hardware or software failures. This is achieved through load balancing, failover mechanisms, and redundancy. 

• Disaster Recovery Plans: Banks develop comprehensive disaster recovery plans that outline procedures for data recovery in the event of natural disasters, system failures, or cyberattacks. 

To further enhance ACID compliance, banks should consider the following precautions: 

• Regular Audits and Compliance Checks: Conduct regular audits and compliance checks to ensure that ACID properties are consistently met. Identify any anomalies and address them promptly. 

• Security Patch Management: Keep database systems and software up to date with security patches to prevent vulnerabilities that could compromise data integrity. 

• Data Encryption and Key Management: Ensure that encryption keys are managed securely, and data encryption protocols are strong and up to date. 

• Monitoring and Alerts: Implement continuous monitoring and alert systems that detect unusual activities, unauthorized access, or potential threats to data integrity. 

• Data Lifecycle Management: Define and enforce data lifecycle management policies, including data retention and disposal, to prevent data accumulation and maintain database performance. 

• Employee Training: Train bank employees on data security, best practices, and the importance of adhering to ACID compliance guidelines. 

• Data Quality Control: Implement data quality control processes to identify and rectify data anomalies and errors. 

• Regulatory Compliance: Stay updated with banking regulations and ensure that the database systems comply with industry standards and legal requirements. 

ACID compliance is fundamental in banking, and banks invest heavily in infrastructure, security, and best practices to maintain data integrity and transactional reliability. Staying vigilant and proactive in addressing evolving threats and challenges is essential for ongoing ACID compliance. 

We at Splenta systems specializes in providing the expertise needed to create cloud-based data storage solutions that are fully compliant with acid standards.

Get in touch with our consultant to develop acid compliant data storage’s on cloud for your organization.

Conclusion 

In the ever-evolving world of data management and application development, data integrity remains a top priority. ACID transactions have been a cornerstone of relational databases, ensuring that transactions occur reliably and without compromising data consistency. As the landscape continues to shift with the rise of NoSQL and distributed systems, new standards like BASE have emerged to address the evolving needs of modern applications. 

Whether you are working with traditional SQL databases or embracing the flexibility of NoSQL, understanding the principles of ACID and BASE transactions is essential for building robust and reliable applications. Data integrity will always be a critical concern, and the knowledge of how transactions work behind the scenes is invaluable in safeguarding your application’s data.