godaddy lock

Multi-thread pessimistic lock, optimistic lock, multi-thread 1. pessimistic lock, as it is called, refers to a conservative attitude towards data being modified by the outside world (including other transactions of the current system, as well as transactions from the external system). Therefore, the data is locked during the entire data processing process. Pessim

Tags: c blog http a COM strongIn the database, concurrency control has optimistic lock and pessimistic lock between, when with optimistic lock compare good when with pessimistic lock?In the actual production environment, if the concurrency is not small, can use pessimistic locking method, this method is very convenient

[Guide: The basic theory of locks used in various large databases is consistent, but there are differences in the implementation. SQL Server emphasizes that the locks are managed by the system. When the user has a SQL request, the system analyzes the request, automatically in satisfying the lock condition and the system performance for the database with the appropriate lock, while the systems are often auto

Reprint: http://blog.csdn.net/sunp823/article/details/49886051The state of the lock: lock-free, biased, lightweight, and heavy-lock.The bias lock applies to scenarios where only one thread accesses the synchronization block.Lightweight locks, competing threads do not block, and are suitable for holding locks for a relatively short period of time. A thread that do

1. application. Lock and application. Unlock are usually paired to lock allCode(Do not lock the assignment to the application ). 2. Lock (OBJ) is used to lock the OBJ object. The OBJ object must be a global object (for example, application ). Application.

Lock, lock 1. view the current Lock ObjectSelect a. owner,A. object_name,B. xidusn,B. xidslot,B. xidsqn,B. session_id,B. oracle_username,B. OS _user_name,B. process,B. locked_mode,C. machine,C. status,C. server,C. sid,C. serial #,C. programFrom all_objects,V $ locked_object B,V $ session cWhere (a. object_id = B. object_id)And (B. process = c. process)Order by 1,

I have never carefully understood the UPDATE lock. I recently saw a problem on the MSDN forum asking about the deadlock issue of heap table UPDATE. The problem is very simple. There are tables and data like this: Create table dbo. tb ( C1 int, C2 char (10 ), C3 varchar (10) ); GO DECLARE @ id int; SET @ id = 0; WHILE @ id BEGIN; SET @ id = @ id + 1; INSERT dbo. tb VALUES (@ id, 'B' + RIGHT (10000 + @ id, 4), 'C' + RIGHT (100000 + @ id, 4 )); END; Per

How to lock a row table database 1 how to lock a row of a table SET transaction isolation level read uncommitted Select * from Table rowlock where id = 1 2. Lock a table in the database Select * from table with (holdlock) Lock statement:SYBASE:Update table set col1 = col1 where 1 = 0;MSSQL:Select col1 from table (tabl

Another mechanism for implementing thread synchronization or mutual exclusion in Java 5 is the use of lock. Lock is more object-oriented than the synchronized method in the traditional threading model.Mutual-exclusion lock –lock (Reentrantlock)A mutex is a lock that can be h

Record LockA single index record is locked, the record lock is always indexed, not the records themselves, even if there is no index on the table, then InnoDB creates a hidden clustered primary key index in the background, so the hidden clustered primary key index is locked. So when an SQL does not take any indexes, it will add an X lock behind each clustered index, similar to a table

Lock (Locking)In the process of implementing business logic, it is often necessary to guarantee the exclusivity of data access. As in the final settlement of the financial system, we want to process the data for a cut-off point in time, and we do not want the data to change again during the settlement process (which may be a few seconds or maybe a few hours). At this point, we need some mechanism to ensure that the data will not be modified in the pro

The recent accidental discovery before the pessimistic lock optimistic lock understanding is wrong, so re-study a bit.1. Pessimistic lockPessimistic lock Introduction (encyclopedia):Pessimistic locking, as its name implies, is a conservative attitude to the data being modified by the outside world (including other transactions currently in the system, as well as

In concurrent environments, you can consider the use of lock mechanisms when resolving shared resource conflict issues. 1. Object Lock All objects automatically contain a single lock. The JVM is responsible for tracking the number of times an object is locked. If an object is unlocked, its count becomes 0. When a task (thread) locks an object for the first time,

Java thread fair lock ReentrantLock (boolean fair), reentrantlock fair lockI. Fair lock 1. Why is there a fair lock? The CPU selects a thread randomly while waiting for the queue to schedule the thread. Because of this randomness, the thread cannot be guaranteed first-come-first-served (the lock controlled by synchroni

Two types of locks are available in the Java Reentrantlock constructor: Create fair and unfair locks (default). The code is as follows:Public Reentrantlock () {Sync = new Nonfairsync ();}Public Reentrantlock (Boolean fair) {Sync = Fair? New Fairsync (): New Nonfairsync ();}In the fair lock, the thread acquires the lock in the order in which they make the request, but in the unfair

lock, after the thread gets the memory lock, other threads can not access the memory, in order to achieve simple synchronization in Java, mutex operation.* Understand this principle to understand why synchronized (this) differs from synchronized (static XXX),* Synchronized is to request memory lock for memory block, this keyword represents an object of class.* S

This article mainly introduced the PHP program in the file lock, mutual exclusion lock, read-write lock using skills analysis, which focuses on the Sync module and pthreads module use examples, the need for friends can refer to. We hope to help you. File lockFull name advisory file lock, which is mentioned in the book

Original: Lock-free data structure (LOCK-FREE data structures)One weeks ago, I wrote an article about the latch (latches) and spin lock (Spinlocks) in SQL Server. The 2 synchronization primitives (synchronization primitives) are used to protect shared data structures in SQL Server, such as pages in the cache pool (via a latch (latches)), and locks in the

A large number of files need to be processed. Using a php process will be slow. How to lock a file when a process reads a file. Do not allow other processes to read and directly skip this step. Do you want to continue reading other processes? Rename the file being read. After reading the file, rename is returned, which is very inefficient .... A large number of files need to be processed. Using a php process will be slow. How to

1. PrefaceMultithreaded programming, we not only want to be able to achieve a logical sequencing between two threads, but also want to two unrelated threads when accessing the same resource, while only one thread can operate on the resources, otherwise there will be unpredictable results.For example, there are two threads need to add 1 to the same counter, we want the result is the counter finally add 2, but may also get to this counter, the first thread to the counter plus 1, but the second thr