Four characteristics of database things-acid

Reprinted from: http://blog.csdn.net/logogcn/article/details/6828531

Transactional: atomicity, consistency, separation, persistence

A thing (transaction) is an execution unit that consists of a sequence of column operations, which are either done or not, and are an inseparable unit of work.

Four basic properties of a Database Thing (ACID)

1. atomicity (atomicity)

It means that all the actions contained in the thing are either done entirely or not (all or none).

2. Consistency (consistency)

Before things start, the database is in a consistent state, and when things end, the database must be in a consistent state.

In the case of bank transfers, consistency requires that the execution of a transaction should not change the sum of the sums of two accounts in a and B. Without this consistency, money will be out of the box, or it may be missing. A transaction should transition a database from one consistent state to another consistent state

3. Isolation (Isolation)

The isolation of transactions requires that the system must ensure that the transaction is not affected by other concurrently executing transactions, but also to achieve the same effect: for any pair of transactions T1 and T2, in the case of the transaction T1, the T2 is either executed before the T1 starts, or after the T1 is complete, Each transaction does not feel a concurrent transaction execution in the system.

4. Persistence (Durability)

Once a transaction is successfully completed, its changes to the database must be permanent, even in the event of a system failure, it is not lost, the importance of the data determines the persistence of things important.

Four characteristics of database things-acid