lock computer

One: Java multi-threaded mutex, and Java multithreading introduce the reason for the bias lock and lightweight lock? --->synchronized of the weight of the lock, that is, when the thread runs to the code block, the program's running level from the user state to the kernel state, to suspend all the threads, so that the CPU through the operating system instructions,

;mysql> INSERT intoReal_tableSELECT * fromInsert_table;mysql> TRUNCATE TABLEInsert_table;mysql>UNLOCK TABLES; The advantage of row-level locks is that they reduce conflict locks when many threads request different records. Reduce change data when a transaction is rolled back. Making it possible to lock a single row of records for a long time. The disadvantage of row-level locks is that they consume more memory than page-level locks and table-l

First, Introduction Before we explain these lock concepts, we need to be clear that these locks are not equivalent to Reentratlock locks in the Java API, which are conceptually, the locking mechanisms that are created in JDK1.6 to optimize the synchronized synchronization keyword. The startup and shutdown policies for these locks can be set by setting the JVM startup parameters, and of course, in general, using the JVM default policy. second, Mark Wo

Tags: style io ar os using SP for data onOracle Lock table row-level lock table-level lock ----row is locked exclusively ----Other users cannot modify this line until a row's lock is released----use the commit or the rollback command to release the lock ----Oracle by using I

> TRUNCATE TABLE insert_table;mysql> UNLOCK TABLES;The advantages of row-level locks are:Reduce conflict locks when many threads request different records.Reduce change data when a transaction is rolled back.Making it possible to lock a single row of records for a long time.The disadvantages of row-level locks are:Consumes more memory than page-level and table-level locks.A lock is a mechanism by which a

Tags: operation unique index nod implementation action hit principle BSP MySQL Lock process detailed (1)-Basics MySQL plus lock process details (2)-about MySQL read comprehension MySQL plus lock process details (3)-about MySQL read comprehension MySQL Lock process detailed (4)-select for Update/

pessimistic lock, optimistic lock, only applicable to update operation In the actual production environment, if the concurrency is not small, can use pessimistic locking method, this method is very convenient and simple to use.However, if the concurrency of the system is very large, pessimistic locking can lead to very large performance problems, so choose optimistic locking method. Pessimistic locking ass

Shared lock "s lock"Also called a read lock, if the transaction T with the data object a plus s lock, then the transaction T can read a but cannot modify a, the other transaction can only a plus s lock, and cannot add x lock, unti

operations on a table, but parallel insertions are not possible, you can insert the records into the staging table and then periodically update the data in the staging table to the actual tables. This can be accomplished with the following command: The code is as follows: mysql> LOCK TABLES real_table Write, insert_table write; Mysql> INSERT into real_table SELECT * from insert_table; mysql> TRUNCATE TABLE insert_table; Mysql> UNLOCK TABLES; Th

accomplished with the following command: mysql> LOCK TABLES real_table Write, insert_table write;Mysql> INSERT into real_table SELECT * from insert_table;mysql> TRUNCATE TABLE insert_table;Mysql> UNLOCK TABLES; The advantages of row-level locks are:Reduce conflict locks when many threads request different records.Reduce change data when a transaction is rolled back.Making it possible to lock a single row o

Tags: key data Purpose value result bidirectional collation coexistence priorityA lock is a mechanism by which a computer coordinates multiple processes or a purely thread concurrently accessing a resource. in a database, data is a resource that is shared by many users in addition to the contention of traditional computing resources (CPU, RAM, I/O). How to guarantee the consistency and validity of data conc

The exclusive lock is also called the Write lock ((eXclusive lock, précis-writers is the x lock), if the transaction T to the data object a plus x lock, then only allow T to read and modify a, no other transaction can be a plus any type of

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 data

shared lock (S lock) and exclusive lock (x Lock) Category: Database 2008-11-07 10:53 4409 people read reviews (2) favorite report Shared lock "s lock"Also called a read lock, if the t

Java synchronized keyword usage and level of Lock: Method Lock, Object lock, Class lock Reproduced from: http://blog.csdn.net/le_le_name/article/details/52348314 Java built-in locks: Each Java object can be used as a lock that implements synchronization, and these locks be

Shared lock "s lock"Also called a read lock, if the transaction T with the data object a plus s lock, then the transaction T can read a but cannot modify a, the other transaction can only a plus s lock, and cannot add x lock, unti

1. Features:The thread that has acquired the lock requests the lock again, which can be obtained directly.2. Realize:Custom internal class Sync, inheriting Abstarctqueuedsynchronizer:2.1. Get lock : Lock ()A, Fair lock:Acquire (1)B, non-fair lock:if (compareandsetstate (0, 1))CAS, the current state is 0, the current th

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 data

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