Question

因此,我要提出一个问题,使我陷于僵局。了解该制度的人可以清楚地说明为什么这种争执正在陷入僵局,但他们告诉我,我应该补充这一点:

SET NOCOUNT ON
SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED

这是否真正是有效的解决办法? 做些什么?

Answer 1

SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED

这将使该系统能够退回非现场数据,包括重复记录和遗失记录。更多阅读,或在此 .

如果你遵循适当的程序,可以调查和确定死亡日,这不是一件大事。当然,扔 read子似乎比较容易,但你在你的总分类账下坐着长时间的路子,并想知道它为什么会坐在,而不是的平衡点和信用额。因此,在你真的贪.之前再读到:<>DIRTY READs ARE INCONSISTENT READS。

如果您希望获得一张排出的jail卡,请上 >snapshotlate :

ALTER DATABASE MyDatabase
SET READ_COMMITTED_SNAPSHOT ON

但是,铭记光是孤立无遗的而不是<>m>,解决了僵局,只是掩盖了这些僵局。适当调查僵局的原因和解决办法始终是适当的行动。

Answer 2

NOCOUNT将不把电网退回到电话申请(即受影响的输电)。

发送标准允许按所示方式提供继承:here。

孤立程度可能有所助益,但你是否希望允许过错?

Answer 3

que 不大可能帮助Imzh

SET NOCOUNT ON

这个问题不会有任何影响。

SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED

您的问询将妨碍大家共同走锁。除了阅读“继承”数据外,还可能导致你对同一行的两读,或者完全取决于其他同时进行的活动。

能否解决你的僵局取决于僵局的类型。如果问题有2名作者由于不按规定提出24小时要求而陷入僵局,那么它就没有任何效果。 (交易1更新浏览量,交易2更新浏览量b,然后是第1部分,要求锁在B和2栏,要求锁在(a)上)

您能否把犯罪论调和僵局成图? (如果你在2005年或之后坐在Q8)

Answer 4

最好的指南是:

Snippet:

Specifies that statements can read rows that have been modified by other transactions but not yet committed。

Transactions running at the READ UNCOMMITTED level do not issue shared locks to prevent other transactions from modifying data read by the current transaction。 READ UNCOMMITTED transactions are also not blocked by exclusive locks that would prevent the current transaction from reading rows that have been modified but not committed by other transactions。 When this option is set, it is possible to read uncommitted modifications, which are called dirty reads。 Values in the data can be changed and rows can appear or disappear in the data set before the end of the transaction。 This option has the same effect as setting NOLOCK on all tables in all SELECT statements in a transaction。 This is the least restrictive of the isolation levels。

In SQL Server, you can also minimize locking contention while protecting transactions from dirty reads of uncommitted data modifications using either:

The READ COMMITTED isolation level with the READ_COMMITTED_SNAPSHOT database option set to ON。 The SNAPSHOT isolation level

。

Answer 5

在不同的方面,可以考虑另外两个方面,这可能有助于。

(1) 指数和国库所用的指数。表格中使用的指数化战略将影响到多少行。如果你采用独特的指数修改数据,你可以减少僵局的可能性。

一种算法——当然不会对所有案件都适用。使用无杀伤人员地雷的具体目标不是全球性的。

The "old" way:
UPDATE dbo.change_table
   SET somecol = newval
 WHERE non_unique_value =  something 

The "new" way:
INSERT INTO #temp_table
    SELECT uid FROM dbo.change_table WITH (NOLOCK)
     WHERE non_unique_value =  something 

UPDATE dbo.change_table
   SET somecol = newval
  FROM dbo.change_table c
       INNER JOIN
       #temp_table t
       ON (c.uid = t.uid)

2) Transaction duration The longer a transaction is open the more likely there may be contention. If there is a way to reduce the amount of time that records remain locked, you can reduce the chances of a deadlock occurring. For example, perform as many SELECT statements (e.g. lookups) at the start of the code instead of performing an INSERT or UPDATE, then a lookup, then an INSERT, and then another lookup. This is where one can use the NOLOCK hint for SELECTs on "static" tables that are not changing reducing the lock "footprint" of the code.

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