ledger locks

A Distributed Lock is needed in recent projects. Considering that the performance of the zookeeper Lock Based on session nodes is insufficient, we want to use redis to implement a distributed lock. After reading several implementation solutions on the internet, I found that they were not rigorous enough. For example, the biggest problem in implementing the locks in Distributed locks using Redis is that the

-- Select, update, and delete locks to be applied for to handle deadlock congestion problems (two update operations) For the update statement, you can simply query the SQL Server first and find the data to be modified. Then, modify the record. The S lock (shared lock) is required for the query action. After finding the record to be modified The U Lock will be applied first, and then the U Lock (update lock) will be upgraded to the X lock (exclusive

the database can we find the factors and bottlenecks that affect the system performance. In this way, we can take appropriate policies to address the bottlenecks and improve the system performance. Concurrency is also a very important concept. It is used to solve the problem when multiple users operate on the same data. Especially for network databases, this feature is even more prominent. It is not enough to increase the processing speed of the database simply by improving the physical speed o

There are several modes of locking in Oracle:0:none1:null Empty2:row-s line Sharing (RS): Shared table locks, Sub share3:row-x Line Exclusive (RX): For row modifications, sub Exclusive4:share shared Lock (S): Prevents other DML operations, Share5:s/row-x shared Row Exclusive (SRX): Block other transaction operations, Share/sub exclusive6:exclusive Exclusive (X): Independent access use, exclusive The types provided by 1.oracle can be queried according

The locks in Java can be divided into object locks, Fang, and class locks by hierarchical points.Java object locks and class Locks: Java's object locks and class locks are basically the

Reentrantlock Source Analysis 1--get unfair lock and fair lock () The most common way: View Code 1, for Reentrantlock need to master the following Reentrantlock creation (Fair lock/non-fair lock) Lock: Lock () Unlock: Unlock () First of all, class structure: Reentrantlock-->lock nonfairsync/fairsync-->sync-->abstractqueuedsynchronizer--> Abstractownablesynchronizer Nonfairsync/fairsync-->sync is the three internal class of Reentrantlock node is an internal class of Abstractqueuedsynchronizer Not

Read Non-REPEATABLE READ Phantom reading Read UNCOMMITTED √ √ √ Read committed X √ √ REPEATABLE READ X X √ Serializable X X X The default transaction isolation level for most databases is read Committed, while the transaction isolation level for MySQL is read repeatedly (Repeatable read). For missing updates, only the serialization (Serializable) level can be co

I. Why should I introduce locks? When multiple users concurrently perform database operations, the following data inconsistency occurs: ◆ Update loss A and B read and modify the same data. The Modification result of one user destroys the Modification result of another user, such as the ticket booking system. ◆ Dirty read User a modified the data, and user B then read the data again. However, user a canceled the data modification and restored the ori

How mysql locks a single tableCopy codeThe Code is as follows:Mysql> lock table userstat read;Mysql> unlock tables;A typical page-level engine is BDB.A typical table-level engine is MyISAM, MEMORY, and ISAM, which was a long time ago.A typical line-level engine is INNODB.-Row locks are the most commonly used in actual applications.Row-level locks have the followi

A database is a shared resource used by multiple users. When multiple users access data concurrently, multiple transactions can access the same data simultaneously in the database. If concurrent operations are not controlled, incorrect data may be read and stored, compromising Database Consistency. Locking is a very important technology for implementing database concurrency control. Before a transaction operates on a data object, it first sends a request to the system to lock it. After the lock,