kiosk 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

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

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

Java Object Header and monitorJava object headers are the basis for implementing synchronized lock objects, and the lock objects used by synchronized are stored in the Java object header.The object header contains two parts: Mark Word and Class Metadata AddressWhere Mark Word stores the object's hashcode, generational age, lock tag bit, and so on by default the f

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:

page level: Engine BDB. Table level: Engine MyISAM, understood to lock the entire table, you can read at the same time, write No Line level: Engine INNODB, a separate row of record lock table level, directly lock the entire table, during your lock, other processes cannot write to the table. If you are a write

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

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

Another lock lock is provided after the JDK1.5. Lockimplementations provide a wider synchronized range of locking operations than can be obtained using 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

　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

performance cannot linearly increase by 3 CLH because the latency of accessing far-memory far exceeds the local memory. CLH (Craig, Landin, and Hagersten locks): A spin lock that ensures no starvation, provides first-come-first-served fairness. The CLH lock is also a scalable, high-performance, fair spin lock based on the list, and the application thread spins

Oracle lock 3: DDL lock, oracle lock 3ddlWhen an ongoing DDL operation is executed or a schema object (Note) is referenced, the Data dcictionary (DDL) Lock is used to protect the definition of the schema object, only a single schema object is locked during DDL operation. The database never locks the entire data diction

Recently encountered multithreading problem, originally only used synchronized method lock, for which the object lock and class lock understanding, but not carefully studied. So go back and check the relevant data for collation. Basic Knowledge First the introduction of object lock (also called method

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

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