InnoDB System Variables Maximum Value 127 The  innodb_undo_tablespaces  variable is deprecated and is no longer configurable as of MySQL 8.0.14. Expect it to be removed in a future release. Defines the number of undo tablespaces used by  InnoDB . The default and minimum value is 2. For more information, see Section 15.6.3.4, “Undo Tablespaces” . When enabled,  InnoDB  uses  fdatasync()  instead of  fsync()  when flushing data to the operating system. Unlike  fsync() , which is used by default,  fdatasync()  only flushes the metadata of accessed files as necessary, providing a performance benefit in certain scenarios. Specifies whether to use the Linux asynchronous I/O subsystem. This variable applies to Linux systems only, and cannot be changed while the server is running. Normally, you do not need to configure this option, because it is enabled by default. The asynchronous I/O capability that  InnoDB  has on Windows systems is available on Linux systems. (Other Unix-like systems continue to use synchronous I/O calls.) This feature improves the scalability of • innodb_use_fdatasync • innodb_use_native_aio 3296 Note Command-Line Format --innodb-use-fdatasync[={OFF|ON}] Introduced 8.0.26 System Variable innodb_use_fdatasync Scope Global Dynamic Yes SET_VAR  Hint Applies No Type Boolean Default Value OFF Command-Line Format --innodb-use-native-aio[={OFF|ON}] System Variable innodb_use_native_aio Scope Global Dynamic No SET_VAR  Hint Applies No Type Boolean Default Value ON