The ACID properties, and the need for each of them are:-

• Consistency: Execution of a TRANSACTION in isolation (that is, with no other transaction EXECUTING concurrently) PRESERVES the consistency of the database. This is typically the responsibility of the application programmer who codes the transactions.
• Atomicity: Either all OPERATIONS of the transaction are reflected properly in the database, or none are. Clearly lack of atomicity will lead to inconsistency in the database.
• Isolation: When multiple transactions execute concurrently, it should be the case that, for every pair of transactions Ti and Tj , it appears to Ti that either Tj finished execution before Ti started, or Tj started execution after Ti finished. Thus, each transaction is unaware of other transactions executing concurrently with it. The user VIEW of a transaction system requires the isolation property, and the property that concurrent schedules take the system from one consistent state to another. These requirements are satisfied by ensuring that only serializable schedules of individually consistency preserving transactions are allowed.
• Durability: After a transaction completes successfully, the changes it has made to the database persist, even if there are system failures.

The ACID properties, and the need for each of them are:-