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The ACID Model in the database


Posted on : 21-11-2011 | By : Amitav C | In : Postgres

What is ACID?


Atomicity – “All or nothing” means the entire transaction fails if any part of a query fails
Consistency – Only valid data is written to database
Isolation – Multiple simultaneous transactions don’t impact each other
Durability – Transactions committed to database will never be lost


Atomicity states that database must follow an “all or nothing” principle. That is every transaction is known to be atomic in nature. If one part of the transaction fails, the entire transaction fails. It is the critical operation that the database management system maintains the atomic nature of transactions.

Consistency states that only valid data is written to the database. If a part of the transaction is will not executed because of whatever reasons, the entire transaction will be rolled back maintaining the consistency rule. On the other hand, if a transaction successfully executes, it will take the database from one state  to another state and will maintain the rule of consistency. So you will not have to worry about the consistency of your database. Your database will always be in a state of its consistency.

Isolation states that for multiple transactions executing at the same time will not impact each other’s execution. Note that the isolation property does not ensure the sequence of the transaction, however, will ensure that they will not interfere with each other.


Durability states that any transaction committed to the database will not be lost. Durability gives the assurance through the use of database backups and transaction logs that facilitate the restoration of committed transactions in spite of any subsequent software or hardware failures.

So, spend some time before you and choose the database for your applications.

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