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
In addition to Spinlock, the Linux kernel also has a spin lock called arch_rwlock_t. Its header file is Qrwlock.h, contained in Spinlock.h, which is called "Queue read/write lock" in the header file. This lock implements a read-write lock using only two member variables. A spinlock, and a shaping
With the development of the Internet, more and more Internet enterprises are confronted with the concurrency security problems caused by the expansion of user volume. This paper mainly introduces several kinds of locking mechanisms common in Java concurrency.1. Bias Lock The bias lock is a mechanism of lock optimization proposed by JDK1.6. The core idea is that i
5000 employees have 10 people, transaction a read all wages for 5000 of the number of 10 people.
At this time
Transaction B Inserts a record with a salary of 5000.
This is, transaction a reads the employee with a payroll of 5000 again, and records 11 people. This creates a phantom read.
4. Reminders
The key to non-repeatable reading is to modify:
The same condition that you read the data, read it again and find that the value is different
The focus of Phantom reading is to add or delete:
Th
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.
Tags: Oracle databaseA DML lock, also called a data lock, is used to ensure that data is complete when multiuser data is manipulated. DML locks prevent conflicting DML and DDL operations from occurring at the same time.DML locks have row locks,tx and table locks (table Locks,tm), and the corresponding locks are automatically requested by different DML operations.Row loc
When InnoDB determines whether a row lock is in conflict, in addition to the most basic is/ix/s/x lock collision judgment, InnoDB also subdivides the lock into the following seed types:
Record Lock (RK)Record locks, lock only one row of index records
Gap
The 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 commonly used MYISAM and INNODB support table-level locks.
The
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
A recently maintained network server encountered performance problems, so it made major changes to the original program framework. Most of the changes are the thread working mode and data transmission mode. The final result is to change the lock usage mode. After some improvement, we can basically achieve
GMB
Network Adapter working at full speed. In
After the performance was up to standard, I was wondering if I could use a more lightweight
Pessimistic lock and optimistic lock in hibernate
Locking)During the implementation of business logic, data access needs to be exclusive. For example, in the daily final computing process of the financial system, we want to process the data at a cut-off time point instead of the settlement process (which may be several seconds, or several hours), and the data changes again. At this point, we need to use som
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
Note: 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 concurrency control (optimistic
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
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
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
The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion;
products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the
content of the page makes you feel confusing, please write us an email, we will handle the problem
within 5 days after receiving your email.
If you find any instances of plagiarism from the community, please send an email to:
info-contact@alibabacloud.com
and provide relevant evidence. A staff member will contact you within 5 working days.