ACID (Atomicity, Consistency, Isolation, Durability) properties are a set of database management principles designed to ensure database transactions' reliability and consistency.

In this blog, we will take a look at each of these properties and try to summarize them with examples.

The ACID properties of a database refer to a set of properties that ensure the reliability, consistency, and durability of data in a database.

These properties are essential for ensuring that data in a database remains accurate, even in the face of failures, such as system crashes or power outages.

They also ensure that database transactions are processed reliably, with the guarantee that even in the event of a failure, the database will remain in a consistent state.

• Atomicity

  Atomicity refers to the property that a database transaction is indivisible. Either all the operations in a transaction are completed, or none of them are completed. In other words, a transaction is treated as a single, indivisible unit of work.

  This ensures that if a transaction fails, the entire transaction is rolled back, and the database remains in a consistent state.

  Atomicity refers to the concept of all-or-nothing when it comes to database transactions.

  For example, if you want to transfer $100 from one bank account to another, the transaction would only be considered complete if both the withdrawal from the first account and the deposit into the second account were successful.

  If either the withdrawal or the deposit fails, the entire transaction is rolled back and the accounts are left in their original state.

• Consistency

  Consistency refers to the property that a database remains in a consistent state, even after a transaction has been completed.

  This means that the database must enforce any constraints and rules that have been defined, such as referential integrity constraints.

  If a transaction would violate any of these constraints, the database must either reject the transaction or ensure that the constraints are still satisfied after the transaction has been completed.

  Consistency ensures that the database remains in a valid state even after multiple transactions.

  For example, if a customer tries to withdraw more money than what is in their account, the database must reject the transaction to maintain consistency.

  Another example is if a database has a rule that a customer can only have one active account, a transaction that attempts to add a second active account for that customer would fail, and the database would remain in a consistent state.

• Isolation

  Isolation refers to the property that a database ensures that the operations of one transaction are isolated from the operations of other transactions.

  This means that even if multiple transactions are executed concurrently, the operations of each transaction are executed as if they are the only transaction in progress.

  This property ensures that the results of a transaction are not affected by the actions of other transactions and vice versa.

  Isolation ensures that each transaction is executed in a separate environment and does not interfere with other transactions.

  For example, if two customers try to withdraw money from the same account at the same time, the database must execute each transaction separately, ensuring that the balance of the account remains consistent.

• Durability

  Durability refers to the property that a database ensures that the results of a transaction are permanently stored in the database, even if the system crashes or there is a power failure.

  This property is usually achieved through the use of database transactions and write-ahead logging.

  Write-ahead logging is a technique where the database logs all changes to the database before they are made, ensuring that the database can be recovered to its previous state in the event of a failure.

  This is achieved through the use of logs, backups, and other methods to ensure that the data is not lost in the event of a system failure.

  Durability ensures that once a transaction is committed, its effects will persist, even in the event of a system failure.

  For example, if a customer makes a transfer, the database must ensure that the changes are permanent and survive even if the system crashes.

In conclusion, the ACID properties of a database ensure the reliability, consistency, and durability of data in a database.

These properties ensure that transactions are executed atomically, the database remains in a consistent state, operations of one transaction are isolated from the operations of other transactions, and the results of a transaction are permanently stored in the database, even in the event of failures.

These properties make databases a powerful tool for managing data and are essential for many applications, such as financial systems, where data accuracy and reliability are critical. By following these principles, databases can ensure that transactions are atomic, consistent, isolated, and durable, providing a stable and reliable environment for data storage and retrieval.

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