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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” . 

• innodb_use_fdatasync 

## Note 

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. 

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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. 

• innodb_use_native_aio 

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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 

