为什么System.Transactions的TransactionScope的默认的IsolationLevel Serializable接口 [英] Why is System.Transactions TransactionScope default Isolationlevel Serializable

问题描述

我只是想知道什么创造了System.Transactions的的TransactionScope ：当一个好理由来使用序列化作为默认的IsolationLevel可能是，因为我想不出任何（它似乎是无法更改通过web / app.config中的默认，所以你总是要设置在你的code）

I am just wondering what a good reason to use Serializable as the default Isolationlevel may be when creating a the System.Transactions TransactionScope, because I cannot think of any (and it seems that you cannot change the default via web/app.config so you always have to set it in your code)

using(var transaction = TransactionScope()) {
    ... // creates a Transaction with Serializable Level
}

相反，我总是写样板code是这样的：

Instead i always have to write boilerplate code like this:

var txOptions = new System.Transactions.TransactionOptions();
txOptions.IsolationLevel = System.Transactions.IsolationLevel.ReadCommitted;

using(var transaction = new TransactionScope(TransactionScopeOption.Required,txOptions)) {
    ... // 
}

任何想法？

推荐答案

事实上序列化是默认来自时候，.NET甚至没有一年（前公布1999年），由DTC（分布式事务处理协调）节目。

The fact Serializable is the default comes from times when .NET wasn't even released (before year 1999), from DTC (Distributed Transaction Coordinator) programming.

DTC使用本机的IsolationLevel 枚举：

DTC uses a native ISOLATIONLEVEL enumeration:

ISOLATIONLEVEL_SERIALIZABLE
  由当前事务读取的数据不能
  由另一个事务被改变，直至当前事务
  饰面。没有新的数据可被插入这将影响当前
  交易。 这是最安全的隔离级别，是默认的，
  但允许并发的最低水平。

.NET 的TransactionScope 是建立在这些技术之上。

.NET TransactionScope is built on top of these technologies.

现在，下一个问题是：为什么DTC定义 ISOLATIONLEVEL_SERIALIZABLE 作为默认事务级别？我想这是因为DTC是围绕1995年设计（1999年之前肯定）。在那个时候，SQL标准是SQL-92（或SQL2）。

Now, the next question is: why DTC defines ISOLATIONLEVEL_SERIALIZABLE as the default transaction level? I suppose it's because DTC was designed around year 1995 (before 1999 for sure). At that time, the SQL Standard was SQL-92 (or SQL2).

和这里是 SQL-92 说，大约成交水平：

And here is what SQL-92 says about transaction levels:

这是SQL事务都有一个READ UNCOMMITTED隔离级别，
  READ COMMITTED，可重复读取，或可序列化。隔离级别
  一个SQL事务的定义在何种程度上的操作对系统蒸发散
  在SQL事务SQL数据或模式是受
  和效果可以影响到SQL的数据或模式在操作
  并发SQL-交易。 SQL-事务隔离级别
  默认情况下序列化。水平可通过显式地设置
  

An SQL-transaction has an isolation level that is READ UNCOMMITTED, READ COMMITTED, REPEATABLE READ, or SERIALIZABLE. The isolation level of an SQL-transaction defines the degree to which the opera- tions on SQL-data or schemas in that SQL-transaction are affected by the effects of and can affect operations on SQL-data or schemas in concurrent SQL-transactions. The isolation level of a SQL- transaction is SERIALIZABLE by default. The level can be explicitly set by the .

并发SQL-事务隔离级别执行
  SERIALIZABLE是保证序列。可序列化exe-
  意外地被定义为并发的操作的执行
  rently执行SQL-交易产生相同的效果
  这些相同的SQL事务的一些串行执行。串行exe-
  意外地是中，每一个SQL事务执行完毕
  先下一SQL事务就开始了。

The execution of concurrent SQL-transactions at isolation level SERIALIZABLE is guaranteed to be serializable. A serializable exe- cution is defined to be an execution of the operations of concur- rently executing SQL-transactions that produces the same effect as some serial execution of those same SQL-transactions. A serial exe- cution is one in which each SQL-transaction executes to completion before the next SQL-transaction begins.

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