function lock

Synchronized is a mutual exclusion lock;Lock is more extensive and includes read/write locksRead/write Lock features:1) Multiple readers can read at the same time2) The writer must be mutually exclusive (only one writer is allowed to write, nor does the reader write at the same time)3) The writer takes precedence over the reader (once the writer is written, the s

the lock concept in MySQLDifferent storage engines in MySQL support different locking mechanisms. For example, the MyISAM and memory storage engine with table-level locks, bdb with a page lock, also supports table-level locks, InnoDB storage engine supports both row-level locks, table-level locks, by default, row-level locks.The MYSQL3 lock features are as follow

the table. The IN lock is used for the table to allow uncommitted read. 2.2.2 DB2 row lock mode In addition to table locks, DB2 also supports row locks in the following ways. Table 2: DB2 database row lock mode 2.2.3 compatibility of DB2 locks Table 3: Compatibility Matrix of DB2 database table locks Table 4: Compatibility Matrix of DB2 database row locks

queue in AQS that "waits for locks. In multithreading, in order to protect competing resources from being operated by multiple threads at the same time, we often need to use locks to protect these resources. In an exclusive lock, a competitive resource can only be accessed by one thread lock at a time point, while other threads need to wait. CLH is the queue that manages these "waiting for locks" threads.

From: http://www.blogjava.net/xylz/archive/2010/07/07/325410.html Next, this article starts with lock. Lock/unlock. In special cases, all programs, APIs, and documents are based on JDK 6.0. Public void java. util. Concurrent. locks. reentrantlock. Lock () Obtain the lock. If the

lock mechanism of a database like a pessimistic lock. Optimistic locking indicates the number of times the current record has been modified (version number) by adding a Count field to the table. The optimistic lock is then implemented by the version number before updating and deleting. Declaring the version number field The version number is the root of the opti

　In the development of distributed cluster system, the thread lock is often not able to support the use of all scenarios, and a new technology scheme distributed lock must be introduced.　　thread Lock: Everyone is not unfamiliar, mainly used to give methods, code block lock. When a method or block of code uses a

thread" directly acquires "lock"; otherwise, call acquire (1) to acquire the lock.Compareandsetstate () is a CAS function that compares and sets the state of the current lock. If the lock has a status value of 0, the lock's state value is set to 1.(Setexclusiveownerthread) The role of Thread.CurrentThread () is to set

MySQL database lock mechanism-MyISAM engine table lock and InnoDB row lockLock concept in MySQL Different storage engines in Mysql support different lock mechanisms. For example, the MyISAM and MEMORY storage engines use table-level locks. BDB uses page locks and table-level locks. the InnoDB Storage engine supports row-level locks and table-level locks, row-leve

Are class locks and object locks conflicting? are object locks and private locks conflicting? Explained by an instance. I. Relevant agreement To clarify the description of the following article, first of all the relevant definitions of the lock involved in this article are as follows: 1. Class Lock: A static and synchronized lock is added to the method in the

Oracle lock 1: DML lock, oracle lock 1dmlDML lock, also known as data lock, is used to ensure data integrity when multiple users operate on data. DML lock prevents conflicting DML and DDL operations at the same time. DML Locks inc

Note: This article is reproduced from http://www.hollischuang.com/archives/914In computer science, a lock is a synchronization mechanism used to forcibly restrict access to resources when executing multiple threads, which is used to guarantee the satisfaction of mutex requirements in concurrency control.As described in the lock mechanism of the database, the database locks can be divided into row-level lock

SNWHERE se.statics# = sn.statics#and NAME like '%cpu used by this session% 'and Se.sid = Ss.sidand ss.status = ' ACTIVE 'And Ss.username is not NULLORDER by VALUE DESC;--Get current session ID, process ID, client ID, etc.SELECT B.sid, B.serial#,a.spid ProcessID, b.process clientpidFrom V$process A, v$session bWHERE a.addr = b.paddr and B.audsid = USERENV (' SessionID ');--Query and display the actual Oracle link in the viewSELECT Osuser,username,machine,programFrom V$sessionORDER by Osuser;--Qu