Transaction Concept _ Four characteristics

1. Transaction Concept _ four characteristics

First, the business

The concept of a transaction : A transaction is a logical set of operations that either completes at the same time or is not completed at the same time .

Management of transactions : By default , the database automatically manages transactions , which is managed by a single statement that is exclusive of a transaction .

If you need to control the transaction yourself, you can also open / commit / rollback the transaction with the following command

Start transaction;

Commit

Rollback

managing transactions in JDBC :

Conn.setautocommit (FALSE);

Conn.commit ();

Conn.rollback ();

SavePoint sp = Conn.setsavepoint ();

Conn.rollback (SP);

Four characteristics of a transaction: the most basic feature of a transaction , a well-designed database can help us ensure that transactions have these four characteristics (ACID)

1. Atomic Nature : atomicity means that a transaction is an inseparable unit of work, and the operations in the transaction either occur or do not occur.

2 consistency So after the end of the transaction ,

Integrity State of the database : When all the data in a database conforms to all the constraints defined in the database , It can be said that the database is an integrity state .

3. isolation : the isolation of transactions means that when multiple users access the database concurrently, the transaction of one user cannot be interfered by other users ' transactions, and the data between multiple concurrent transactions is isolated from each other.

4. Durability : persistence refers to the fact that once a transaction is committed, it changes the data in the database to be permanent, and then it should not have any effect even if the database fails.

Isolation :

The design of the database as a single -threaded database prevents all thread-safety issues and naturally ensures isolation . But if the database is designed like this , then the efficiency will be extremely low . .

Transaction Concept _ Four characteristics