ledger locks

About the locks in the MySQL InnoDB Storage Engine Recently, I encountered many lock problems. After solving these problems, I carefully read the books about locks and sorted them out as follows: 1. Lock type The Innodb Storage engine implements the following two standard row-level locks: The S lock allows a transaction to read a row of data. X lock allows a t

1. The difference between synchronized and lockThere are some drawbacks to synchronizing blocks that are implemented using the SYNCHRONIZED keyword:(1) There is only one type of lock(2) thread gets locked or blocked(3) lock is implemented in the Java language level based on the CAS spin mode to achieve the lock, under the concurrency conditions, its performance is relatively better than synchronized.In order to solve the various problems, a more complex lock-thread locking was proposed later. Th

In the process of learning or using Java, the process encounters a variety of lock concepts: Fair lock, unfair lock, spin lock, reentrant lock, biased lock, lightweight lock, heavyweight lock, read-write lock, mutex wait. Here to tidy up the various locks in Java, if there is a lack of hope that we are in the bottom of the message to discuss.Fair lock and non-fair lockA fair lock is when multiple threads are waiting for the same lock and must be locke

Explain how to query and unlock Oracle lock tables and explain how to unlock oracle locksDatabase Operation statement category DDL: database mode definition language; Keyword: create DML: data manipulation language; keywords: Insert, delete, and update DCL: Database Control Language, Keyword: grant, remove DQL: Database Query Language, Keyword: selectWhen Will oracle tables be locked? DML locks can be divided into row

Read-Write Locks and mutexes (mutexes) are similar and are another thread synchronization mechanism, but are not POSIX-standard and can be used to synchronize individual threads in the same process. Of course, if a read-write lock is stored in a memory area shared by several processes, it can also be used to synchronize between processes, and the mutex is either locked or unlocked, and only one thread can lock it at a time. Read and write

of the class, and the class can have both synchronous and non-synchronous methods.4) If you have synchronous and non-synchronous methods, the non-synchronous method can be freely accessed by multiple threads without a lock limit.5) When the thread sleeps, the lock it holds will not be released.6) Threads can obtain multiple locks. For example, in the synchronization method of one object to invoke the synchronization method of another object, the sync

The nature of Oracle row-level locks (I) three major components of the single-instance Oracle locking mechanism www.2cto.com locking mechanism: ① resource structure Oracle for each resource requiring "concurrent access, both use a Data structure in SGA to describe it. This structure is called resource structure. The data structure has three members: owner, waiter, and converter are three pointers pointing to the linked list composed of lock structures

examples to demonstrate how to use DB2 for Linux ?, UNIX ?, And Windows? Of db2pdAnd db2pdcfgUtility to complete the task. Used for Lock monitoringdb2pdOption db2pdIs a utility for monitoring various DB2 database activities and troubleshooting. It is an independent utility released with the DB2 engine since DB2 V8.2. Its appearance and functions are similar to Informix.onstatUtility.db2pdIs executed in an optional interactive mode from the command line. The utility runs very fast because it

1. Lock 1) appeared after version 1.5, Java.util.concurrent.locks.Lock 2) The lock implementation provides a wider range of locking operations than is possible with synchronized methods and statements. This implementation allows for a more flexible structure that can have very different properties and can support multiple related Condition objects. A lock is a tool that controls the access of multiple threads to a shared resource. Typically, a lock provides exclusive access to a shared resource

In multithreaded programming, shared variables need to be locked. However, frequent locking can have a significant effect on program efficiency. In some scenarios where read and write less, it is clearly not necessary for multiple threads to read data if they are mutually exclusive. So the read-write lock was born.Lock rules for read and write locks:1 If there is no write lock, then multiple threads can read the lock at the same time, and if there is

Reproduced http://blog.csdn.net/yusiguyuan/article/details/14161225 The synchronization technology between threads mainly focuses on mutex locks and condition variables. The combination of condition variables and mutex can well handle the synchronization problem between threads waiting for conditions. For example, if there are two variables X, Y needs to synchronize among multiple threads and start different thread execution sequence based on the siz

Problem description: Our applications adopt a mechanism of shared memory and read/write locks to achieve concurrent access to multiple processes. However, we found that there was a problem with the read/write locks during the test, the locks we use are pthread_rwlock_rdlock and pthread_rwlock_wrlock. Symptom: Pthread_rwlockattr_setpshared ( ATTR, pthread_process

Transactions and locks have the following features: A transaction is a unit of work, either completely or completely.Transactions ensure operation consistency and recoverabilityEach Transact-SQL statement can be a transaction.The actual transaction is a user-defined transaction, which includes a series of operations or statements.In a multi-server environment, user-defined distributed transactions are used to ensure operation consistency.Lock is a mea

My experience on ORACLE Data locks, my experience on oraclePart of the post content is for the attachments in The Post (a warrior's understanding about the lock), Understanding/question,Before reading this post, read this article.First, let's talk about the various types of locks: Shared locks, arrange it, and share the exclusive

How to Improve the Performance of Java locks (1) We try our best to find a solution to the problems encountered by our products, but I will share with you several common technologies in this article, these technologies include separating locks, parallel data structures, protecting data rather than code, and narrowing down the scope of the lock. These technologies enable us to detect deadlocks without any t

I have translated an article about the Java read/write lock, because I have never read the related content of the read/write lock before. Here, even if I have learned and translated it, it may not be accurate! Well, let's talk less about it. Let's get started. The read/write lock is more profound than the "Lock in Java" article. Imagine that you have an application that reads/writes certain resources, and the number of write operations is less than the number of read operations. Two threads that

shielding, BKL (big kernel lock), rwlock, brlock (only included in the 2.4 kernel), RCU, and seqlock (only in the 2.6 kernel ). (1) spin lock) Spin lock is a kind of lock designed to prevent multi-processor concurrency. It is applied to interrupt processing and other parts. For a single processor, to prevent the concurrency in the interrupt processing, you can simply disable the interrupt without the need for spin locks. The spin lock can only be hel

5. Complete the variable If one task in the kernel needs to send a signal to notify another task of a specific event, using the completion variable is a simple way to synchronize the two tasks. The completion variable is represented by the structure completion, in Declare_copletion (my_comp ); Dynamic initialization during runtime: Int_completion (my_comp ); On a specified completion variable, the task to wait for calls wait_for_completion () to wait for a specific event. When a specific event

Today the order out of a stock oversold problem, looking for a long time before locating the reason, before using rails also rarely used transactions and locks, here to introduce them. Why use a transaction transaction is a unit of concurrency control, a user-defined sequence of actions. In simple terms, multiple operations within a transaction are either not executed or executed together. Transactions can help developers ensure data consistency in th

the talent can go in (online to find the metaphor, very image). But I want to be concurrency is embarrassing, haha.Basic types of LocksOperations on the database can be summarized into two types: Read and write.When multiple transactions read an object at the same time, there is no conflict. simultaneous reading and writing, or simultaneous writing, can create conflicts. therefore, in order to improve the concurrency performance of the database, two kinds of