drm 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

1.1.1.three write lock downgrade for read-write lock applicationReentrantreadwritelock also features write-lock demotion, which has some relationship to reentrant sex. (1) you can downgrade to read lock when holding a write lock. (2) You cannot upgrade to a write

The more obvious the advantage of threads in the multi-core era over the past month, the learning of multi-threaded programming is also on the agenda. But more and more people are stuck in the thread Quagmire, and finally they are totally confused. There are more and more deadlocks and more abnormal data. In the concurrency test, let one threadProgramEmployees are overwhelmed. "I have nothing to do in my own programming environment, and there will be no errors in single-step debugging. When two

File lockThe name is advisory file lock, which is mentioned in the book. This type of lock is more common, such as MySQL, PHP-FPM Boot will have a PID file records the process ID, this file is a file lock. This lock prevents a process from running repeatedly, such as limiting the execution of a task every minute when

PHP program in the file lock, mutex, read and write the use of skills analysis, File lockFull name advisory file lock, which is mentioned in the book. This type of lock is more common, such as MySQL, after php-fpm boot, there will be a PID file record the process ID, this file is a file lock. This

Page level: Engine BDB.Table level: Engine MyISAM, understood to lock the entire table, can read at the same time, write NoRow level: Engine INNODB, single row of records plus lockTable level, which locks the entire table directly, and other processes cannot write to the table during your lock. If you are writing a lock, other processes are not allowed to readRow

Latch locks and tlock (transaction locks), DML lock rules, and deadlock analysis in MySQL.I. The relationship between latch and TlockLatch: Designed to protect the correctness of critical resources, such as protecting the memory pages that are being used from being destroyed.There is no deadlock detection mechanism, a lightweight lock, and a memory page or memory sharing variable when the object is in effec

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

First of all explain: Method lock and Object lock is said to be a thing, that is, only method lock or object lock and class lock two kinds of locks The author uses the easy language to explain the complex technology so thoroughly, learn, spread. Original address: http://zhh

Tags: nod tom research htm attribute reference serial environment controlRefer to http://www.jb51.net/article/50047.htm "MySQL row level lock, table level lock, page level lock Details" Page level: Engine BDB.Table level: Engine MyISAM, understood to lock the entire table, can read at the same time, write NoRow level:

Tags: lock src proc nbsp BSP log own. com sqlOne, table-level lock 1. Read lock,lock table t_student Read, add read lock, so that other Sessiona and sessionb can not modify the data, just read the data. Show processlist; View process, modify the state is waiting for the tab

Pessimistic lock (Pessimistic Lock), as the name implies, is very pessimistic, every time to take the data when they think others will change, so every time when the data are locked, so that other people want to take this data will block until it gets the lock. Traditional relational database in the use of a lot of this locking mechanism, such as row locks, table

Lock synchronization lock -- thread synchronization, Lock synchronization -- threadLock-synchronization Lock Lock is a powerful thread synchronization mechanism provided by Java 5-achieve synchronization by displaying and defining synchronization

First introduce some optimistic lock and pessimistic lock:Pessimistic lock: Always assume the worst case, every time to take the data when they think others will change, so every time when the data are locked, so that other people want to take this data will block until it gets the lock. Traditional relational database in the use of a lot of this locking mechanis

Hibernate lock mechanism. Let's make a summary today. Hibernate locks include pessimistic locks and optimistic locks. 1. pessimistic lock It refers to a conservative attitude towards data being modified by the outside world. Assume that another customer may be able to access the same data at any time. To maintain the consistency of data operations, the data is locked at the database level, it depends on the