Based on the principle and implementation of concurrent control of Informix

Based on the principle and implementation of concurrent control of Informix In the modern database management system, it is very important to implement concurrent control, especially in high concurrency environments.Informix is a powerful relationship database management system that provides a series of mechanisms to achieve efficient concurrency control.This article will introduce how to implement these principles and provide the necessary code examples and related configurations on the basis of explaining the principle of Informix's concurrent control principles. In Informix, implementation of concurrent control depends mainly on the following principles: 1. Lock mechanism: Informix uses the lock mechanism to manage concurrent access to the database.Lock is a mechanism that protects resources. It can prevent other transactions from reading or modifying resources until the current transaction release lock.Informix provides shared locks and locks, which can choose appropriate lock levels as needed. 2. Affairs isolation level: In INFORMIX, the interaction between transactions can be controlled by setting transaction isolation levels.Common quarantine levels include unsurremmming, submitted, repeated read and serialization.Each level has different lock strategies and concurrent control mechanisms. 3. Snapshot isolation: In order to achieve efficient concurrent control, Informix introduced the snapshot isolation mechanism.Snapshot isolates the consistency snapshot of databases, maintains the consistency of data during the execution of transactions, and prevent conflicts between affairs. Now we will introduce how to implement concurrent control in Informix in detail. First, we need to create an example table to demonstrate the principles and implementation of concurrent control.Suppose we have a table called "Employee", which contains fields such as "EMP_ID", "EMP_NAME" and "Salary".We will use the following SQL statements to create this table: sql CREATE TABLE employee ( emp_id INT PRIMARY KEY, emp_name VARCHAR(50), salary DECIMAL(10, 2) ); Next, we will use Informix's lock mechanism to implement concurrent control.Informix provides the following types of locks: -Shared lock: Multiple transactions can obtain shared locks at the same time, and can read the locked resources, but cannot be modified. -ExClusive Lock: Only one transaction can get the lock of his lock, and you can read and write the locked resources. We can use the following code example to demonstrate the use of the lock: sql BEGIN WORK; LOCK TABLE employee IN SHARE MODE; SELECT emp_name, salary FROM employee WHERE emp_id = 1; -- Perform some operations COMMIT WORK; In the above code, we use the `Lock Table` statement to get the shared lock and use the` Share Mode` parameter to specify the lock mode.Then we can perform reading operations.Finally, we use the `Commit Work` statement to release the lock.Similarly, you can also use the `Exclusive Lock` to get his lock. In addition to locking mechanisms, we can also set up transaction isolation levels to control the behavior between transactions.You can use the following statements to set the transaction isolation level: sql SET ISOLATION TO <isolation_level>; Among them, the `isolation_level` can be one of the following options:` Read uncommitted`, `Read committed`,` repeatable read` or `serializable`. Finally, in order to achieve snapshot isolation, we need to set the isolation level of the affairs to the `RepeaTable Read` or higher level, and use the following code example to demonstrate its use: sql BEGIN WORK ISOLATION LEVEL REPEATABLE READ; SELECT emp_name, salary FROM employee WHERE emp_id = 1; -- Perform some operations COMMIT WORK; In the above code, we use the `Begin Work` statement to start a transaction, and set the isolation level to the` Repletable Read`.We can then perform reading and operation, and finally use the `Commit Work` statement to submit transactions. In short, through Informix's lock mechanism, transaction isolation level and snapshot isolation, we can achieve efficient concurrent control.By using these mechanisms correctly and following the relevant encoding and configuration, we can ensure the reliability and performance of the database in the high concurrent environment.