【MySQL 5.7 Reference Manual】15.4.11 Undo Tablespace（Undo表空间）

15.4.11 Undo Tablespace（Undo表空间）

An undo tablespace comprises one or more files that contain undo logs. Undo logs exist within undo log segments, which are contained within rollback segments. By default, rollback segments are physically part of the system tablespace. However, rollback segments can reside in separate undo tablespaces. An undo tablespace is created when the undo log is separated from the system tablespace using the innodb_undo_tablespaces and innodb_undo_directory configuration options.

一个undo表空间由一个或多个包含undo logs文件组成。Undo日志存在于undo日志段中，而undo日志段被包含在回滚段中。在默认情况下，回滚段物理上是系统表空间的一部分。然而，回滚段可以驻留在单独的undo表空间中。当使用innodb_undo_tablespaces和innodb_undo_directory配置项将undo日志从系统表空间中独立出来时，会创建一个undo表空间。

For more information, see Section 15.7.7, “Storing InnoDB Undo Logs in Separate Tablespaces”.

更多信息，请参考15.7.7，“在单独的表空间中存储InnoDB Undo日志”。