数据库事务转载基础二：oracle事务隔离级别

Oracle 支持的 2 种事务隔离级别 Read committed ， Serializable

来自 oracle 官方网站的 Read committed ， Serializable 的解释

Isolation Level	Description
Read committed	This is the default transaction isolation level. Each query executed by a transaction sees only data that was committed before the query (not the transaction) began. An Oracle query never reads dirty (uncommitted) data. Because Oracle does not prevent other transactions from modifying the data read by a query, that data can be changed by other transactions between two executions of the query. Thus, a transaction that runs a given query twice can experience both nonrepeatable read and phantoms.
Serializable	Serializable transactions see only those changes that were committed at the time the transaction began, plus those changes made by the transaction itself through INSERT , UPDATE , and DELETE statements. Serializable transactions do not experience nonrepeatable reads or phantoms.

Isolation Level

Description

Read committed

This is the default transaction isolation level. Each query executed by a transaction sees only data that was committed before the query (not the transaction) began. An Oracle query never reads dirty (uncommitted) data.

Because Oracle does not prevent other transactions from modifying the data read by a query, that data can be changed by other transactions between two executions of the query. Thus, a transaction that runs a given query twice can experience both nonrepeatable read and phantoms.

Serializable

Serializable transactions see only those changes that were committed at the time the transaction began, plus those changes made by the transaction itself through INSERT , UPDATE , and DELETE statements. Serializable transactions do not experience nonrepeatable reads or phantoms.

2 者的区别也是来自官方网站

summarizes key differences between read committed and serializable transactions in Oracle.

Table 13-2 Read Committed and Serializable Transactions

	Read Committed	Serializable
Dirty write	Not possible	Not possible
Dirty read	Not possible	Not possible
Nonrepeatable read	Possible	Not possible
Phantoms	Possible	Not possible

上面的 2 个表来自 http://download-west.oracle.com/docs/cd/B19306_01/server.102/b14220/consist.htm

数据库事务转载基础二：oracle事务隔离级别相关推荐

数据库事务转载基础二：MySQL事务隔离级别详解
SQL标准定义了4类隔离级别,包括了一些具体规则,用来限定事务内外的哪些改变是可见的,哪些是不可见的.低级别的隔离级一般支持更高的并发处理,并拥有更低的系统开销. Read Uncommitted(读 ...
数据库事务转载基础一:oarcle事务
Oracle事务 2010-11-29 14:22 前言首先思考一个问题:如果对数据库进行了多次修改,如果前面的修改成功,后面修改时发生了意外,怎么办? 案例:以银行转账为例. 有帐户表记录如下: ...
数据库事务的4大特性与隔离级别
本篇讲诉数据库中事务的四大特性(ACID),并且将会详细地说明事务的隔离级别. 如果一个数据库声称支持事务的操作,那么该数据库必须要具备以下四个特性: ⑴ 原子性(Atomicity) 原子性是指事务 ...
一天十道Java面试题----第四天（线程池复用的原理------＞spring事务的实现方式原理以及隔离级别）
这里是参考B站上的大佬做的面试题笔记.大家也可以去看视频讲解!!! 文章目录 31.线程池复用的原理 32.spring是什么? 33.对Aop的理解 34.对IOC的理解 35.BeanFactor ...
笔记47-徐数据库引擎中基于行版本控制的隔离级别
笔记47-徐数据库引擎中基于行版本控制的隔离级别 MSSQL隔离级别 READ UNCOMMITTED(未提交读),相当于(NOLOCK) READ COMMITTED(已提交读,默认) REPEA ...
oracle的隔离级别
一.事务和隔离级别事务的概念:事务是把对数据库的一系列操作都看做一个整体,要么全部成功,要么全部失败,利用事务我们可以保证数据库的完整性,事务具有原子性. 隔离级别:隔离级别定义了事务与事务之间的隔 ...
数据库脏读、事务的四大特性、四大隔离级别、三大范式
一.数据概念 1.脏数据所指的就是未提交的数据.也就是说,一个事务正在对一条记录做修改,在这个事务完成并提交之前,这条数据是处于待定状态的(可能提交也可能回滚),这时,第二个事务来读取这条没有提交的数 ...
【Redis】事务不保证原子性、没有隔离级别
一.回顾mysql事务四大属性原子性(Atomicity)原子性是指事务包括的所有操作要么成功,要么全部失败回滚一致性(Consistency) 事务执行之前和执行之后都必须处于一致性状态.举例来 ...
数据库基础知识ACID，隔离级别RC,RR,RU,SERIALIZABLE，Phantom Rows幻读，解决幻读，脏读dirty read
ACID A atomicity, C consistency,I isolation, and D durability的缩写,这些特性和事务是紧密联系的,InnoDB事务的特点和ACID原则紧密联 ...

数据库事务转载基础二：oracle事务隔离级别

数据库事务转载基础二：oracle事务隔离级别相关推荐

最新文章

热门文章