Wednesday, 16 March 2011

Database ACID Acronym

This is something I knew, but like a lot of things forgot... and I got asked but couldn’t remember - although I could remember the theory behind it. There is a really good full description of this on wikipedia, so the table below is just something to jog your memory.

What ACID Means

A stands for atomicity, which means that given a transaction containing multiple SQL statements, then when the transaction completes, all or non of the statements must be committed to the database.

C stands for consistency. This means that a transaction will take the database from one consistent state to another, in order words, only valid data can be written to the database.

I stands for isolation, which means that an operation cannot access data that has been modified by another operation’s transaction, until that transaction has been committed to the database.

D stands for durability. This means that once a transaction has been committed, then the database won’t loose that transaction’s data.

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