isolation levels in db2

There are four levels of database isolation, as described in the book High performance MySQL: Then tell me how to modify the transaction isolation level: 1. Global modification, modify Mysql.ini configuration file, at the end Plus Copy Code code as follows: #可选参数有: read-uncommitted, read-committed, Repeatable-read, SERIALIZABLE. [Mysqld

transactions that read data do not prevent other transactions from writing to the data. transactions that write data do not prevent SNAPSHOT transactions from reading data. in the rollback phase of database recovery, if you attempt to read data that is locked by another transaction that is being rolled back, the SNAPSHOT transaction will request a lock. the SNAPSHOT transaction is blocked until the transaction has finished rolling back. when a transaction is authorized, the lock is released im

Label:There are four database isolation levels, as described in the "high-performance MySQL" Book:Then talk about how to modify the transaction isolation level:1. Global modification, modify the Mysql.ini configuration file, at last add1 #可选参数有: read-uncommitted, read-committed, Repeatable-read, serializable.2 [mysqld]3 transaction-

the disadvantage of defining with natural language, which may easily lead to ambiguity ).11. The definition of serializable SQL is quite clear, but that table is easy to mislead everyone. This is why Oracle and other products that only implement Snapshot Isolation are also mistaken for support for serializability.12. Classic locks, write locks, two-phase locks, and corresponding isolation

Acid is the cornerstone of database theory. It defines four properties required by a theoretically reliable database: atomicity, consistency, isolation, and persistence. Although these four attributes are important, isolation is the most flexible. Most databases provide some available isolation levels, and many databas

must be completed by the storage engine. Table lock: Lock a table Page lock: Lock a page Row lock: Lock a row The finer the granularity, the better the concurrency. That is, row locks have the best concurrency, but they must be supported by the storage engine. Read uncommitted (read uncommitted): allows dirty reads, that is, reads from uncommitted transaction changes in other sessions (read committed ): only submitted data can be read. Most databases such as oracle repeatable read are repeat

results of successful transaction commits, the database is said to be in a consistent state. If a database system fails in operation and some transactions have not yet been completed, some of the modifications made to the database have been written to the physical database, and the database is in an incorrect state, or an inconsistent state. 3, isolation. Execution of one transaction cannot interfere with other transactions. That is, the operations w

In-depth understanding of four isolation levels of Mysql and four mysql 1. What is a transaction first? A transaction is a series of strict operations in an application. All operations must be completed successfully. Otherwise, all changes made in each operation will be revoked. That is to say, a transaction is atomic, and a series of operations in a transaction either succeed or do not. There are two types

multi-granularity blocking mechanism with intention locks to control concurrency and ensure data consistency. Its DML lock (Data lock) is divided into two levels (granularity): Table-level and row-level. Generally, DML operations only obtain the intention lock (RS or RX) at the table level, and the real blocking granularity is still at the row level; DB2 also uses a multi-granularity blocking mechanism wit

Label:V. Lock and TRANSACTION isolation levels Transaction ISOLATION level The simple thing is that when the transaction is activated, the control transaction causes the locking of the SQL statement to be kept multiple, and the extent of the impact, in order to prevent multi-person access, the data query within the transaction error. Setting the transaction