Exclusive locks prevent access to a resource by concurrent transactions 排他鎖( x鎖)可以防止并發(fā)事務(wù)對(duì)資源進(jìn)行訪問。
Shared locks allow concurrent transactions to read select a resource under pessimistic concurrency control 共享鎖( s鎖)允許并發(fā)事務(wù)在封閉式并發(fā)控制(請(qǐng)參閱
Conversely , a query holding a sch - s lock blocks a concurrent transaction that attempts to acquire a sch - m lock 相反,持有sch - s鎖的查詢將阻塞嘗試獲取sch - m鎖的并發(fā)事務(wù)。
When one transaction holds a lock on an item , no concurrent transaction can read and / or modify this item 當(dāng)一個(gè)事務(wù)對(duì)一個(gè)數(shù)據(jù)擁有了鎖,那么其他并發(fā)事務(wù)則無法對(duì)它進(jìn)行讀或者寫。
Because of this , queries are blocked when a concurrent transaction holds a sch - m schema modification lock on the table 因此,當(dāng)并發(fā)事務(wù)持有表的sch - m (架構(gòu)修改)鎖時(shí),將阻塞查詢。
A transaction is a unit of isolation and each occurs separately and independently of concurrent transactions 事務(wù)是一個(gè)隔離單元,并發(fā)事務(wù)中的每個(gè)事務(wù)在發(fā)生時(shí)都相互分離,彼此獨(dú)立。
Modifications made by concurrent transactions must be isolated from the modifications made by any other concurrent transactions 由并發(fā)事務(wù)所作的修改必須與任何其他并發(fā)事務(wù)所作的修改隔離。
Imagine that two concurrent transactions both read a row , one writes to it and commits , and then the second writes to it and commits 有兩個(gè)并發(fā)事務(wù)同時(shí)讀取同一行數(shù)據(jù),然后其中一個(gè)對(duì)它進(jìn)行修改提交,而另一個(gè)也是修改提交。
In addition , it brings forward the method to the concurrent transactions " s cooperative process , solve the underlying conflication problems 另外,在協(xié)議棧的實(shí)現(xiàn)過程中,對(duì)多個(gè)并發(fā)事務(wù)的協(xié)調(diào)處理提出了自己的解決思路,有效地克服了潛在的會(huì)話沖突問題。
The microsoft sql server database engine locks resources using different lock modes that determine how the resources can be accessed by concurrent transactions Microsoft sql server數(shù)據(jù)庫引擎使用不同的鎖模式鎖定資源,這些鎖模式確定了并發(fā)事務(wù)訪問資源的方式。