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Definition: ACID Properties
ACID refers to atomicity, consistency, integrity and durability. Basically these four properties decides whether a database is reliable or not. If a database fails to meet any of these criteria then it’s not a good reliable database.
The description of all these properties is given as follows:
Atomicity: All the transactions made in a database are atomic, i.e. it follows all or nothing rule. It means either full update is made on thedatabase or the update is not done at all. If there is any type of failure before committing a transaction, the database goes to its earlier state by rollback.
Consistency: Only those data which meets the rules of database columns will be written into the database. If some update violates such rules then the transaction commit will fail and it will rollback to its earlier state.
Isolation: The database is not impacted by multiple transactions occurring at a single point of time. Suppose Ram and Ashish are going to withdrawing money from Jack’s account. Jack has got $ 1000 in his account and both logs in at the same time to withdraw money. Database isolation ensures that one user has to wait until other commits the changes. In other words for writing into the database a user needs to have an exclusive key and this takes care of isolation.
Durability: Durability is the feature that ensures that any change won’t be lost after database commit has been done.