ledger locks

Server Objectiveperformance, how to maximize the performance of the database is the problem that every DBA needs to face, in a small amount of data running fly, and in a large number of data is slow as a snail, such things have you ever met it? How to improve the concurrency access performance of the database better? Yes, "lock", the key to solving the problem. Preliminary knowledgeLock mode, most content excerpt from SQL Server 2000 Books OnlineIf you are already familiar with the type of SQL S

final time is acceptable to the user within the range can be.1. Optimistic lock and pessimistic lock Pessimistic lock (pessimistic lock), as the name implies, is very pessimistic, every time to get the data are thought that others will be modified, so every time when the data will be locked, so that others want to take this data will block until it gets the lock. The traditional relational database inside the use of a lot of this locking mechanism, such as row

Table-level locks have a total of five modes, as shown below.Row-level exclusive lock (row Exclusive, short rx Lock)When we do DML, we automatically add the RX lock on the table being updated, or you can explicitly add the RX lock on the table by executing the lock command. In this lock mode, other transactions are allowed to modify other rows of data in the same table through DML statements, or the lock command adds RX

How MySQL locks a single table Copy Code code as follows: Mysql>lock table Userstat Read; Mysql>unlock tables; The typical page-level representative engine is BDB. The typical representative engine for the table level is myisam,memory and ISAM, a long time ago. The typical line-level representative engine is InnoDB. -the most used in our actual application is the row lock. The advantages of row-level

The locking prompt indicates that holdlock retains the shared lock until the transaction is completed, instead of releasing the lock immediately when the corresponding table, row, or data page no longer needs it. Holdlock is equivalent to serializable. Do not issue a shared lock or provide an exclusive lock. When this option is enabled, it may read uncommitted transactions or a group of pages that are rolled back during reading. Dirty reads may occur. Applies only to select statements. Paglock u

. Http://msdn.microsoft.com/en-us/library/aa213029 (v=sql.80). aspx HTTP://WWW.CNBLOGS.COM/PYQ228/ARCHIVE/2012/05/26 /2519447.html Third, the solutionQuarantine----to localize data (that is, use unshared data, thread-exclusive), thread-safe identification of unchanging data--try to use constant locking--to lock variable data that has to be shared Iv. optimistic locking strategy-conflict detectionOptimistic lock policies are usually based on some version of the data tag. To detect "lost upda

In a previous essay, simply mention the isolation level in SQL Server. The isolation level of SQL Server is implemented through the locking mechanism. Now go deeper and talk about locks in SQL Server.Before you begin, define the prerequisites:1. The implementation of isolation level is actually locked on different resources.2. Every access to a database (CRUD) We call it a transaction (a block of statements in the Begin Tran,commit Tran|rollback Tran,

Lock mechanism series for SQL Server:lock mechanism for SQL Server (i)--Overview (types and scopes of locks)lock mechanism for SQL Server (ii)--Overview (lock compatibility and resources that can be locked)lock mechanism for SQL Server (iii)--Overview (Locks and transaction isolation levels)lock mechanism for SQL Server (iv)--Overview (impact of various transaction isolation levels)Lock: Popular speaking is

Deeply understand the principles and usage of Yii2.0 optimistic and pessimistic locks, and deeply understand yii2.0 This article introduces the principles and usage of Yii2.0 optimistic and pessimistic locks, and shares them with you as follows: Web applications often face multi-user environments. In this case, concurrent write control becomes a skill that almost every developer must master. In a concurrent

In modern multi-user multi-task systems, it is inevitable that multiple users access a shared object simultaneously. This object may be a table, row, or memory structure, to solve the data security, integrity, and consistency problems caused by multi-user concurrent access, a mechanism is required to serialize the concurrent access to these shared resources, oracle locks can provide this function. Before a transaction operates on an object, it first s

The concept of 11.5.1 Lock Lock (Lock) is a restriction of access to resources in a multiuser environment. Mechanism when a data source is locked, the data source has a certain access limit. We call this data source "locked". In SQL Server, you can lock on the following objects: Data row (ROW): a single row of data in a data page; Index row (key): a single row of data in an index page, which is the key value of an index; Page: A page is the basic unit of SQL Server Access data, w

Hibernate and Database LocksOne, why use the lock? To understand the reasons for the existence of the lock mechanism, the first thing to know is the concept of the transaction.A transaction is a series of related operations to a database that must have acid characteristics: A (atomicity): either all succeeds or all is withdrawn. C (consistency): To maintain consistency in the database. I (Isolation): When different transactions operate the same data, have to have their own data spa

Objective: We all know the nature of the transaction, in order to maintain these properties, especially the consistency and isolation of the database, the use of locks is generally used in this way. At the same time, the database is a high concurrent application, there will be a large number of concurrent access, if the lock excessive, will greatly reduce the concurrent processing capacity. So for the lock processing, it can be said that the database

The following article describes the operating mechanism of Oracle locks. We all know that in modern multi-user and multi-task systems, when multiple users access a shared object at the same time, the probability is very high. This object may be a table, row, or memory structure. To solve the data security, integrity, and consistency problems caused by concurrent access by multiple users, a mechanism is required. To serialize the concurrent access to t

Fundamentals of Database LocksIn order to ensure the data is finished and consistent, the database system adopts the lock to realize the isolation of the transaction. The basic theory of locks used in various large databases is consistent, but there are differences in the implementation.From a relationship locked by a concurrent transaction, it can be divided into shared locks and exclusive