November 26, 2018
Database Talk: What is ACID compliance?
To have optimal transaction control, a database system must be ACID compliant, which stands for the following properties: Atomicity, Consistency, Isolation, Durability. The definitions of the ACID properties are:
Atomicity: A transaction must be completed in its entirety or not at all. If a transaction aborts in the middle, all operations up to that point must be completely nullified.
Consistency: A transaction must transform a database from one consistent state to another consistent state. In other words, all data in a database must work as a state machine. The database must ensure all data is consistent at all times with all rules.
Isolation: Each transaction must occur independently of other transactions occurring at the same time. In other words, queries and transactions always run at a point in time. You can query data while many other users are changing data and you will not see their changes, and they will not see each other’s changes.
Durability: Committed transactions must be fully recoverable in all but the most extreme circumstances. Write-ahead logs provide absolute data durability until data is eventually written into permanent data and index files.
The ACID properties are intended to guarantee valid database transactions, even if there are network errors, disruptions, hardware failures, etc. For this reason, ACID-compliant databases are important for organizations in many different types of industries, especially those who conduct monetary transactions, handle time-sensitive data, or manage/monitor data in manufacturing, transportation or energy production. ACID compliance can also play an important role in data management in mission-critical operations in IoT environments.
Here is a real-world example: ACID compliance is critical for financial institutions because it prevents the unpleasant situation of paying out the same money twice due to inconsistent transaction processing. Not having an ACID-compliant database could also lead to customer service / public relations nightmares if deposited money is unable to be accessed due to lost transactions, conflicting updates, repeated updates or double-read records.
In healthcare, it is critical that a laboratory information system has an ACID-compliant database for the handling of personal medical data. A database that provides accurate and timely information could be the difference between successful and unsuccessful treatment of a patient. Imagine the problems that could occur when a doctor and a nurse simultaneously update a patient’s chart and wipe out each other’s changes because the database cannot isolate transactions. Other examples include when a nurse forgets to enter vital information and the database accepts the transaction because it does not enforce business rules or when the database fails to record a drug dose because it is not durable.
It is easy to see why financial and healthcare would need ACID, but what about everyone else? ACID compliance is valuable outside of these industries, and it is a rare case where it is not critical or beneficial. In short, ACID keeps the data in the database accurate. If accurate data is a requirement of a database operation, then the database should be ACID compliant.
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