lasso lock

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,

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

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

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

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

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

Hibernate supports two types of locking mechanisms:The "Pessimistic lock (pessimistic Locking)" and "optimistic Lock (optimisticlocking)" are usually called. Pessimistic lock implementation, often rely on the database provided by the lock mechanism (also only the database layer provides a

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 Lock Manager hash table (via a spin lock (Spinlock)). Next you will se

Lock (Locking)In the process of implementing business logic, it is often necessary to ensureexclusivity 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 to have some mechanism to ensure that the data will not be modified by the out

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

Hibernate supports two types of locking mechanisms:The "Pessimistic lock (pessimistic Locking)" and "optimistic Lock (optimisticlocking)" are usually called.Pessimistic lock implementation, often rely on the database provided by the lock mechanism (also only the database layer provides a

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

MYSQL unlock and lock Table introduction, mysql unlock lock table MySQL lock OverviewCompared with other databases, MySQL locks are relatively simple. The most notable feature is that different storage engines support different locks. For example, the MyISAM and MEMORY storage engines use table-level locking. The BDB storage engine uses page-level locking ), howe

One: Pessimistic lockPessimistic lock, that is, regardless of whether there is a multi-threaded conflict, as long as there is such a possibility, on each access is locked, locking will lead to the contention between the lock, there will be a fight to win or lose, the loser waits.Syncrhoized is an exclusive lock, that is, the thread that occupies the

MySQL lock usage-table-level lock mechanism is an important feature of a database that is different from the file system and an effective way to manage concurrent access. MySQL locks include table-level locks, page-level locks, and row-level locks. Table-level locks are the most granular locks in MySQL. They are easy to implement and consume less resources. They are supported by most MySQL engines. The most

MySQL lock Blocking analysis, mysql lock Blocking During routine maintenance, threads are often blocked, resulting in slow database response. Let's take a look at how to obtain which thread causes blocking. Blog: http://blog.csdn.net/hw_libo/article/details/39080809 1. Environment Description RHEL 6.4 x86_64 + MySQL 5.6.19 Transaction isolation level: RR 2. Test process 3. view the

There's this scenario in the recent project 1. When generating a file, because many users have the right to generate, to prevent concurrent, resulting in the result of the production of errors, need to build the process of locking, only allow a user in a time to operate, this time need to use the lock, the operation of the process of locking up. 2. Cache failure may cause instantaneous majority of concurrent requests to penetrate the database at the t

Data locking is divided into two methods, the first one is called pessimistic lock, the second is called optimistic lock. What is pessimistic lock, pessimistic lock as the name implies, is the conflict of data to take a pessimistic attitude, that is, assuming that the data will certainly conflict, so when the data bega