24 lines
1.2 KiB
Markdown
24 lines
1.2 KiB
Markdown
---
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categories:
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- Databases
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tags: [relational-databases]
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---
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# ACID principle
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> A database is a collection of organised data that can be efficiently stored, sorted, and searched.
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How the data is organised will often determine the _type_ of database used. There are many different types of database; some examples of the different types are relational, object-orientated, graphical, NoSQL, and distributed. All should meet the principles of ACID.
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To ensure the integrity of a database, each change or transaction must conform to a set of rules known as ACID:
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- **atomicity**
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- when changing data within a database, if any part of the change fails, the whole change will fail and the data will remain as it was before the change was made; this is a safeguard that prevents partial records being created.
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- **consistency**
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- before data can be changed in a database, it must be validated against a set of rules
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- **isolation**
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- databases allow multiple changes at the same time, but each change is isolated from others
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- **durability**
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- once a change has been made, the data is safe, even in the event of system failure
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> Databases will have mechanisms for **backup**, **distribution**, and **redundancy**, to ensure data is not lost.
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