两段锁协议 两阶段封锁协议：要求每个事务分两个阶段提出加锁和解锁申请， 增长阶段：事务可以获得锁，但不能释放锁。 缩减阶段：事务可以释放锁，但不能获得新锁。 两阶段封锁协议保证冲突可串行化，因为若事务都遵守两阶段封锁协议，则调度的优先图中无环。 将各个事务根据它们的封锁点进行排序，这个顺序就是事务的一个可串行性次序。 两阶段封锁协议不保证不发生死锁。 两阶段封锁协议不保证不发生级联回滚。

业务场景：关联不同数据库中的表的查询 比如说，要关联的表是：机器A上的数据库A中的表A && 机器B上的数据库B中的表B。 这种情况下，想执行“select A.id,B.id from A left join B on ~~~;“那是不可能的，但业务需求不可变，数据库设计不可变，这就蛋疼了。。 解决方案：在机器A上的数据库A中建一个表B。。。 这当然不是跟你开玩笑啦，我们采用的是基于MySQL的federated引擎的建表方式。 建表语句示例： CREATE TABLE `table_name`(......) ENGINE =FEDERATED CONNECTION='mysql://[

MySQL数据库-事务、锁及SQL优化

Many popular database management systems implement a multiversion concurrency control algorithm called snapshot isolation rather than providing full serializability based on locking. There are well-known anomalies permitted by snapshot isolation that can lead to violations of data consistency by interleaving transactions that would maintain consistency if run serially. Until now, the only way to prevent these anomalies was to modify the applications by introducing explicit locking or ...

DB - Eris - Coordination-Free Consistent Transactions Using In-Network Concurrency Control.pdf Distributed storage systems aim to provide strong consistency and isolation guarantees on an architecture that is partitioned across multiple shards for scalability and replicated for fault tolerance. Traditionally, achieving all of these goals has required an expensive combination of atomic commitment and replication protocols – introducing extensive coordination overhead.

DB - Fast and General Distributed Transactions using RDMA and HTM.pdf Recent transaction processing systems attempt to leverage advanced hardware features like RDMA and HTM to significantly boost performance, which, however, pose several limitations like requiring priori knowledge of read/write sets of transactions and providing no availability support. In this paper, we present DrTM+R, a fast in-memory transaction processing system that retains the performance benefit from advanced hardware

DB - Making Snapshot Isolation Serializable.pdf Snapshot Isolation (SI) is a multiversion concurrency control algorithm, first described in Berenson et al. [1995]. SI is attractive because it provides an isolation level that avoids many of the common concurrency anomalies, and has been implemented by Oracle and Microsoft SQL Server (with certain minor variations). SI does not guarantee serializability in all cases, but the TPC-C benchmark application [TPC-C],

This paper describes our experience implementing PostgreSQL’s new serializable isolation level. It is based on the recently-developed Serializable Snapshot Isolation (SSI) technique. This is the first implementation of SSI in a production database release as well as the first in a database that did not previously have a lock-based serializable isolation level. We reflect on our experience and describe how we overcame some of the resulting challenges, including the implementation of a new lock ...

数据库系统原理：BDB7 数据库事务管理.ppt

Oracle数据库学习 讲解包括试题和答案