idn locks

Understanding mysql locks (1) Overview of locks compared with other databases, MySQL locks are relatively simple. The most notable feature is that different memory engines support different locks, however, mysql memory engines use three types of locking mechanisms: row locking, table locking, and table locking. MyISAM

Transactions are used to ensure data consistency (integrity), and locks are used to ensure data concurrency (control the concurrency of multiple transactions) (concurrency ). The higher the lock level, the database concurrency may be affected. The lower the lock level, the better the database concurrency. The usage of locks in JDBC, JTA, and container management transactions is basically the same, and there

people, transaction a read all wages for 5000 of the number of 10 people.At this timeTransaction B Inserts a record with a salary of 5000.This is, transaction a reads the employee with a payroll of 5000 again, and records 11 people. This creates a phantom read.The key to non-repeatable reading is to modify:The same condition that you read the data, read it again and find that the value is differentThe focus of Phantom reading is to add or delete:The same conditions, the 1th and 2nd readings of

(1) to obtain the lock wait condition, you can analyze the table lock contention on the system by checking the table_locks_waited and table_locks_immediate status variables :; + -------------------------- + ---------- + | Variable_name | Value | + ---------------------------- + ---------- + | Table_locks_imme (1) to obtain the lock wait condition, you can analyze the table lock contention on the system by checking the table_locks_waited and table_locks_immediate status variables :; + -----------

Overview:Shared locks, also known as read locks, referred to as the S-lock, as the name implies, a shared lock is multiple transactions for the same data can share a lock, can access the data, but can only read can not be modified.Exclusive locks, also known as write locks, referred to as the X-Lock, as the name implie

Appendix: The previous period of time to learn the next InnoDB lock related knowledge, lock and transaction has a general understanding, here do a small summary. 1.INNODB Transaction and lock relationships. The two features that distinguish InnoDB from MyISAM are InnoDB support for transactions and support for row locks. The transaction requires the acid characteristics of a set of SQL statements, and in order to avoid concurrent updates to a row of

1 monopoly and sharing of locksThe lock mode provided by Java and the package is divided into exclusive and shared locks, in exclusive lock mode, only one thread can hold the lock at a time, Reentrantlock is the exclusive mutex. Shared locks allow multiple threads to acquire locks concurrently and concurrently access shared resources, such as: Readwritelock. AQS'

Label:From a large class, locks in SQL Server can be categorized as follows:Shared lock (S lock): used to read the lock added by the resource. A resource that has a shared lock cannot be modified. Shared locks are read by default and are released immediately. For example, if I read 100 data, I can imagine reading the first one, releasing the first one immediately, then locking the second data, releasing the

Label:A recent stress test in a project has encountered a deadlock problem with the database, in short, the following code causes a deadlock at the SERIALIZABLE isolation level: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 SELECT@findCount=COUNT(id) FROMMyTable WHERE[fk_related_id][emailprotected]IF (@findCount > 0) BEGIN ROLLBACK TRANSACTION RETURNERROR_CODE ENDINSERTINTOMyTable ([fk_related_id],…) VALUES(@Argument,…)COMMITTRANSACTION RETURNSUCCESS_CODE In the process o

To ensure data consistency and performance in concurrent operations, HBase has a wide variety of efficient reentrant locks, including row-level rowlock, mvcc,region-level read and write locks, store-level read and write locks, memstore-level read and write locks, and so on. 1, row-level lock Rowlock In HBase, the rowlo