【MySQL 5.7 Reference Manual】15.4.13 Redo Log（Redo日志）

15.4.13 Redo Log （Redo日志）

15.4.13.1 Group Commit for Redo Log Flushing （基于 组提交的 Redo日志刷新）

The redo log is a disk-based data structure used during crash recovery to correct data written by incomplete transactions. During normal operations, the redo log encodes requests to change InnoDB table data that result from SQL statements or low-level API calls. Modifications that did not finish updating the data files before an unexpected shutdown are replayed automatically during initialization, and before the connections are accepted. For information about the role of the redo log in crash recovery, see Section 15.18.1, “The InnoDB Recovery Process”.

redo日志基于磁盘的数据结构，在崩溃恢复期间用于纠正不完整事务所写入的数据。在正常操作情况下，redo日志编码请求以改变InnoDB表数据，这些数据来自于SQL语句或低级API调用的结果。如果在意外关闭之前更新数据文件的操作没有结束，这些修改在初始化期间（连接被接收接受之前）会自动重新执行。

By default, the redo log is physically represented on disk as a set of files, named ib_logfile0 and ib_logfile1. MySQL writes to the redo log files in a circular fashion. Data in the redo log is encoded in terms of records affected; this data is collectively referred to as redo. The passage of data through the redo log is represented by an ever-increasing LSN value.

默认情况下，redo日志物理上表现为磁盘上的一堆文件，名为ib_logfile0和ib_logfile1。MySQL以循环方式写入redo日志文件。redo日志中的数据按照受影响的记录进行编码；这些数据整体被用于redo。数据穿过redo日志的通道用一个不断增长的LSN值表示。

For related information, see:

相关信息，请参考：

- Section 15.6.1, “InnoDB Startup Configuration”

- 章节15.6.1，“InnoDB启动配置”

- Section 9.5.4, “Optimizing InnoDB Redo Logging”

- 章节9.5.4，“优化InnoDB Redo日志”

- Section 15.7.2, “Changing the Number or Size of InnoDB Redo Log Files”

- 章节15.7.2，“修改InnoDB Redo日志文件的数量或大小”