MySQL realizes data self-recovery technology

MySQL realizes data self-recovery technology

MySQL is a popular relational database management system. Due to its efficient and stable characteristics, it is widely used in major enterprise-level applications and websites. During operation, the MySQL database is prone to failure due to various reasons, such as power outage, software failure, hardware damage, network interruption, etc., resulting in data loss, which may cause great losses to enterprises and users. Therefore, to ensure data integrity and availability, MySQL has introduced self-recovery technology to cope with this situation.

1. MySQL data recovery

Before discussing MySQL self-recovery technology, we need to know how the recovery mechanism in MySQL works. MySQL data recovery recovers data by executing logs. The transaction log is a type of MySQL log that records any changes made to the database, whether before a process exits successfully or after a failed exit. When a failure occurs, the transaction log is used to reverse all operations before the failure to achieve data recovery.

Reliable storage devices are the key to log recovery. Only when data is correctly written to persistent storage can data recoverability be guaranteed. In MySQL, you can use the InnoDB storage engine, which uses two files to store data and logs: one is a shared table space file, used to store table and index data; the other is a log file, used to store redo log and undo log . These two logs are key components for MySQL to achieve data self-recovery.

2. MySQL’s self-recovery technology

The two log files in MySQL, redo log and undo log, are the key to achieving self-recovery. Redo Log records all modification operations that have not been committed on the disk and is the main means of recovering data. Undo Log records the undoing of modification operations on data. It is a supplement to Redo Log and is used to roll back data.

When MySQL restarts, the redo log file will be checked and uncommitted operations will be re-applied to the data, thus restoring all future visible modification operations. When implementing this data recovery method, InnoDB uses some techniques to ensure data consistency.

First of all, InnoDB uses buffer pool technology to cache data in memory. When the data is modified, it will be written to the redo log file. Even if the data has not been submitted to the disk, it will be temporarily stored in the memory. In this way, during recovery, the modification operations can be re-applied through the redo log file. In addition, InnoDB also uses a write-ahead log delivery mechanism to ensure that the data recorded in the redo log is written to the disk first, thus ensuring that the data recorded in the redo log can be recovered when the system crashes or goes down.

Secondly, Undo log is used to provide rollback operations. If a power outage or other failure occurs before the transaction is submitted, since the data has not been submitted and the modification operations in the redo log have not been applied, the redo log must be restored. The data is not sufficient to recover the data. At this time, you need to use Undo log to perform rollback operation. The Undo log records a copy of all data modified by the transaction. When the transaction is rolled back, InnoDB will use the data in the Undo log to restore the data to the state before the transaction started.

MySQL also provides a recovery mode called automatic recovery mode, which is automatically activated when starting MySQL, allowing MySQL to be restored to any moment before the snapshot that has been created and saved. In automatic recovery mode, MySQL will use redo log and undo log to recover data.

3. Conclusion

In enterprise-level applications and large websites, the security and stability of data are crucial, so the database management system needs to be able to quickly respond when problems arise in the data. recover. MySQL implements data self-recovery technology by using log files to record and recover data, ensuring that data can be recovered immediately when problems occur. The InnoDB storage engine provides a variety of recovery methods, including the use of buffer pools, write-ahead log shipping, and other methods to ensure data integrity and availability, providing efficient and reliable data management services for enterprise-level applications and large websites.

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