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
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
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
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
reorganization output format is//lureturn 0;}The compilation appears stray ' \241 ' in the program, the reason is the double quotation marks in Word, copied into the text file, and should have the English double quotation marks, should re-use the English input method double quotation marks. Exit_failure's header file is Stdlib.hMutual exclusion LockA mutex is a thread synchronization method similar to the POSIX semaphore, which essentially acquires a lock
There are two basic types of blocking: Exclusive lock (x Lock) and shared lock (S-lock). The so-called X-Lock, which is the transaction T to data a plus x lock, allows only transaction T to read and modify data a,... The so-called
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:
Mutex lock, deadlock and recursive lock, mutex lock Recursion1. Mutex)
In the last section, we talked about thread security. Thread Synchronization ensures that multiple threads can securely access competing resources. The simplest synchronization mechanism is to introduce mutex locks. The mutex lock introduces a statu
Https://www.cnblogs.com/qjjazry/p/6581568.html2600433554963791First 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 re
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
Java Day one article June 21 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
Tag: is set ODB full ROM wait ima margin fallbackI. When to use a table lockFor InnoDB tables, row locks should be used in most cases. In individual special transactions, you might consider using table locks (recommended).1. Transactions need to update most or all of the data, the table is larger, the default row lock not only makes the transaction inefficient, may cause other transactions for a long time lock
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
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
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
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