how to lock ssn

Written in front, in fact, the type and scope of database locks are affected by a variety of factors, such as database isolation level, SQL statements, whether to use primary keys, indexes, and so on. Can see the blog: http://www.cnblogs.com/zhaoyl/p/4121010.html LearnThis section describes the types of locks used by InnoDB. Shared Lock (S) and exclusive lock (X) Intent

Lock Interface Locks are used to control how multiple threads access shared resources, in general, a lock prevents multiple threads from accessing shared resources at the same time (but some locks allow multiple threads to access shared resources concurrently, such as read-write locks). Prior to the lock interface, the Java program was locked by the Synchronized

Add by Zhj: This question did not give a satisfactory answer at the end, I have the same confusion with the questioner. Also, see mysql transaction isolation level, lockWhy is optimistic locking more efficient than pessimistic lock?Title: "The Collection" Why optimistic locking efficiency is higher than pessimistic lock? Sending station: Drink from (May 19, 2008 12:29:00 Monday), the station letter☆────────

This section is mainly about the implementation of read-write locks.As mentioned in the previous section, Readwritelock appears to have two locks: readlock/writelock. If it's really two locks, how do they affect each other?In fact, the realization of lock in Reentrantreadwritelock is done by Java.util.concurrent.locks.ReentrantReadWriteLock.Sync. This class looks familiar, in fact it is a subclass of Aqs, a similar structure that exists in Countdownla

Innodb row lock source code learning (1), innodb row lock source code Innodb is the most popular storage engine in mysql databases. Compared with other storage engines, innodb supports transactions and row-level locks. Today, I would like to share with you the basic knowledge of innodb row lock implementation. Due to the large length, the article will be expanded

This chapter introduces the lock Acquisition Mechanism of "fair lock" (the fair lock in this article refers to the fair lock of mutex lock), including: for basic concepts, refer to the Code to obtain the fair lock (based on JDK1.7

level to be completely isolated, a bit of concurrency ...). Therefore, SQL Server's default read commited is a good choice to strike a balance between isolation and concurrency. SQL Server passes the lock, just like a traffic light at a crossroads, to tell all concurrent connections that at the same time those resources can be read and those resources can be modified. As mentioned earlier, the query itself is not a gentleman, so it needs to be superv

Lock Lock IntroductionLock lock Mechanism is a new locking mechanism after JDK 5, unlike the built-in lock, the lock lock must be explicitly declared and the lock is released in the app

The previous sections mainly talk about atomic operations. As for some problems or traps related to atomic operations, they will be explained in the final summary. Starting from this chapter, we will spend a small amount of time talking about the lock mechanism. In the previous chapter, we talked about the lock mechanism and some related concepts and design ideas for atomic operations. In the next article,

Web applications tend to face multi-user environments, where concurrent write control is almost a skill that every developer must master. This paper mainly introduces the principle and use of Yii2.0 optimistic lock and pessimistic lock, hoping to help everyone. In a concurrent environment, it is possible to have dirty reads (Dirty read), non-repeatable reads (unrepeatable read), Phantom reads (Phantom read

Turn from: http://blog.csdn.net/javazejian/article/details/75043422 From "Zejian's blog." Related articles: Deep understanding of Java type information (class object) and reflection mechanism Deep understanding of Java Enum Types (enum) Deep understanding of Java Annotation Types (@Annotation) Deep understanding of the Java Class loader (ClassLoader) Deep understanding of the synchronized implementation principle of Java concurrency Java concurrent Programming-non-

Get an unfair lock (based on jdk1.7.0_40)Unfair locks and fair locks the process is the same on the method of acquiring locks, and their differences are mainly expressed in the "mechanism of trying to acquire locks". Simply put, the "fair lock" is a fair policy every time it tries to acquire a lock (according to the wait queue), while the "unfair

Tags: check log eric Share blog exclusive pessimistic lock good usesql-optimistic lock, pessimistic lock in the concurrency Every time you write a blog, the first sentence is this: the programmer is very hard, in addition to writing procedures, but also to write a blog! Of course, hope that the future day, a boss see this blog, to your programmer staff pay bar! B

Reprint Please indicate the source: http://blog.csdn.net/ns_code/article/details/17487337 Simple use of lock lock The new lock mechanism--java.util.concurrent.locks explicit mutex in Java 5: The Lock interface, which provides a more extensive locking operation than synchronized. The

The last tool in the lock is introduced from this section: read-write Lock (Readwritelock).Reentrantlock implements a standard mutex, which is the notion that only one thread can hold a lock at a time, or the so-called exclusive lock. This feature has been emphasized in the previous chapters. Obviously this feature red

Mysql Innodb Lock Mechanism and mysqlinnodb Lock MechanismLatch and lock Latch can be considered as a lock in an application. It can be called a latch (lightweight lock) because it requires a very short lock time. If the

Every time you write a blog, the first sentence is this: the programmer is very hard, in addition to writing procedures, but also to write a blog! Of course, hope that the future day, a boss see this blog, to your programmer staff pay bar! Because the programmer's world is silent except bitter force. Most of the programmers in my eyes do not love to talk, silently bear the great pressure of programming, in addition to technical exchanges, they do not want to be good at communicating with others,

Basic ConceptsIn this chapter, we will explain the principle of "thread access to Fair lock", and we need to understand a few basic concepts before explaining it. The following are all based on these concepts, which may be tedious, but from these concepts, you can see some of the architecture of the Java lock, which is helpful for us to know about locks.1. AQS -refers to the Abstractqueuedsynchronizer class

Tags: share highlight inno ADE by SWA multiple update one Objective A lock is a mechanism by which a computer coordinates multiple processes or threads concurrently accessing a resource, and in a database, data is a resource that is shared by many users in addition to contention for traditional computing resources such as CPU, RAM, I/O, and so on. How to guarantee the consistency and validity of data concurrent access is a problem that all da

Go to: http://blog.sina.com.cn/s/blog_6d7fa49b01014q7p.htmlMany people ask this question, what does the Linux kernel do to provide a variety of synchronization lock mechanisms? Traced is actually due to the existence of multiple processes in the operating system concurrent access to shared resources, resulting in the race between processes. These include the SMP system we know, the competing resources between multiple cores, the competition between si