lock computer

Why locks (concurrency control) are required. In a multiuser environment, multiple users may update the same record at the same time, which can create a conflict. This is the famous concurrency problem. Typical conflicts are:(1) Missing update: One transaction update overwrites the update result of other transactions, that is, the so-called update is lost. For example: User A changes the value from 6 to 2, and User B changes the value from 2 to 6, then user a loses his update. (2) Dirty read:

I. The background of the spin lock proposedBecause some resources in a multiprocessor system environment are limited and sometimes require mutually exclusive access (mutual exclusion), a lock mechanism is introduced, and only the process that acquires the lock can obtain access to the resource. that is, only one process can acquire a

[ADB command Article 3] What should I do if I forget my mobile phone password (access permission password or lock screen password ?, Adb lock screenThe access restriction password is forgotten, or the lock screen password is forgotten. As a result, some programs (such as text messages, address book, and other important programs) cannot be opened, affecting normal

Description: 1, personal technology is not a drop, also did not write threads in the project, the following are all based on their own understanding of the written. Therefore, only for reference and hope to point out the different views. 2, actually want to put the code of GitHub posted out, but still recommended in the beginner you write more personally, it is not posted out.I. BASIC INSTRUCTIONSClass, Object: ... (Don't know what to say, imaginative achievement here inexpressible >. Class lock

Http://www.infoq.com/cn/articles/java-memory-model-5 deep understanding of the Java Memory Model (v)--lock Http://www.ibm.com/developerworks/cn/java/j-jtp10264/Java Theory and Practice: a more flexible and scalable locking mechanism in JDK 5.0 http://blog.csdn.net/ghsau/article/details/7481142 1, Synchronized Declaring a block of code as synchronized has two important consequences, usually the code has atomicity (atomicity) and visibility (visibilit

The previous article introduces the lock that protects memory structure or variable in MySQL source code, and here we begin to introduce the table lock in MySQL transaction.Note 1: On the implementation of the table lock, the structure of "mutex+condition+queue" is used to implement the table lock function of concurren

Tags: read-only and tle sele generation process external HTTPS openNote: This article is reproduced from http://www.hollischuang.com/archives/934As described in the lock mechanism of a database, the task of concurrency control in a database management system (DBMS) is to ensure that the same data in the database is accessed simultaneously without disrupting the isolation and uniformity of the transaction and the consistency of the database.Optimistic

Previous continuedA murder caused by a lock-free message queue: How to be a real programmer? (a)--ground: CauseA murder caused by a lock-free message queue: How to be a real programmer? (b)--month: Spin lockParallel spaceIn the copy of the above line I stopped first, is considered to occupy a position, although I know how to write, but the feeling is still very messy.I suddenly thought, since so tangled, so

Prior to Java5.0, only synchronized (built-in lock) and volatile. The display lock Reentrantlock is introduced after Java5.0. Reentrantlock OverviewThe Reentrantlock is a reentrant lock, which differs from the built-in lock, which needs to display the lock and unlock fo

With the frontline synchronization only know the Synchronize keyword, then know that there is a lock, why also have a lock to achieve synchronization? Synchronized's limitations occupy the lock thread waiting for IO or other reasons to be blocked, without releasing the lock, Read and read can also conflict when other t

Oracle lock 1: DML lockDML lock, also known as data lock, is used to ensure data integrity when multiple users operate on data. DML lock prevents conflicting DML and DDL operations at the same time. DML Locks include Row Locks (TX) and Table Locks (TM). Different DML operations will automatically request the correspond

This article from: http://blog.163.com/hbu_lijian/blog/static/126129153201261722410353/ Kernel synchronization measures (for Linux kernel) To avoid concurrency and prevent competition. The kernel provides a set of Synchronization Methods to protect shared data. Our focus is not to introduce the detailed usage of these methods, but to emphasize the difference between these methods and them.The synchronization mechanism used in Linux has been continuously improved since 2.0 to 2.6. From the initia

A bloodcase caused by a lock-free Message Queue: how to be a real programmer? (2) -- month: spin lock, queue spinPrefix A bloodcase caused by a lock-free Message Queue: how to be a real programmer? (1) -- location: Cause A bloodcase caused by a lock-free Message Queue: how to be a real programmer? (2) -- month: spin lo

In the database lock mechanism, the task of concurrency control in a database management system (DBMS) is to ensure that multiple transactions simultaneously access the same data in the database without disrupting the isolation and uniformity of the transaction and the consistency of the database. Optimistic concurrency control (optimistic lock) and pessimistic concurrency control (pessimistic

One: OverviewCompared with other databases, MySQL's locking mechanism is relatively simple, and its most notable feature is that different storage engines support different locking mechanisms. For example, the MyISAM and memory storage engines use table-level locks (table-level locking), InnoDB storage engines support row-level locks (row-level locking) and table-level locks, but row-level locks are used by default.MySQL main two types of lock charact

How to set the screen lock page for the new Win10 autumn creative version, win10 autumn creative screen lock In the new version of Windows 10 creative creators in autumn, you can set the display of xiaona on the screen lock page. You can use this function to search for the corresponding features. How can you set this function, let's take a look. On the Windows

How to change the screen lock page in Win10 logon screen background and win10 logon screen lock After the official version of windows10th anniversary is updated, the screen lock page and background of Windows can be automatically changed. You can also use a custom background image to change the background image of the Windows 10 logon interface. Next, let's take

Small knitting computer is ThinkPad, the operating system is 64-bit Win7. When you enter uppercase letters, there is always a hint on the display, and you are not prompted whether it is uppercase or lowercase when you enter it. I'm not comfortable with typing my password, always showing the case lock and Number lock icon on the desktop. As shown in figure

In Java multithreading, you can use the keyword synchronized to implement a mutex between threads. After JDK1.5, a thread concurrency library java.util.concurrent is provided to manipulate multiple threads, including java.util.concurrent.atomic and Java.util.concurrent.lock. Atomic can realize the atomic operation of data or variable, and lock can achieve thread mutual exclusion, can realize read-write lock

Turn InnoDB row-level locksInnoDB Row-level locksCategory: Database 2013-03-13 16:40 1745 people read comments (0) favorite reports Nnodb lock mode and lock methodInnoDB implements the following two types of row locks.? Shared Lock (S): Allows a transaction to read one line, preventing other transactions from acquiring an exclusive