Pedro Arantes

ACID (Database Systems)

ACID (database systems) stands for atomicity, consistency, isolation, durability.
Zettelkasten, April 26th, 2021.


  • ACID (database systems) stands for atomicity, consistency, isolation, durability.

  • Andreas Reuter and Theo Härder coined the acronym ACID in 1983.

  • They're a set of database transactions intended to guarantee data validity.

    • Data validity is guaranteed even if errors or power failures happen.
  • Transaction is a sequence of database operations that satisfies the ACID properties.

  • The four properties:

    • Atomicity: guarantees that each transaction (multiple operations) is considered a single "unit." A transaction succeeds if all operations also succeed. If only one operation fails, the whole transaction also fails.

      • An atomic system must guarantee this property in all scenarios, including power failures, errors, and crashes.
    • Consistency: ensures that transactions can only bring the database from a valid state to another.

      • It maintains the database invariants and constraints. For example, only numbers can be written in a property that is a number.
    • Isolation: ensures that concurrent execution of transactions leaves the database as if the same transactions were executed sequentially.

      • The effects of an incomplete transaction cannot be visible by other transactions.
    • Durability: once the transaction is committed, it will remain even in the case of a system failure.


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