Tablespaces CREATE UNDO TABLESPACE  tablespace_name  ADD DATAFILE ’ file_name .ibu’; SELECT TABLESPACE_NAME, FILE_NAME FROM INFORMATION_SCHEMA.FILES WHERE FILE_TYPE LIKE ’UNDO LOG’; 3061 Prior to MySQL 8.0.14, increasing the  innodb_undo_tablespaces  setting creates the specified number of undo tablespaces and adds them to the list of active undo tablespaces. Decreasing the  innodb_undo_tablespaces setting removes undo tablespaces from the list of active undo tablespaces. Undo tablespaces that are removed from the active list remain active until they are no Prior to MySQL 8.0.14, additional undo tablespaces are created by configuring the innodb_undo_tablespaces  startup variable. This variable is deprecated and no longer configurable as of MySQL 8.0.14. A MySQL instance supports up to 127 undo tablespaces including the two default undo tablespaces created when the MySQL instance is initialized. To view undo tablespace names and paths, query  INFORMATION_SCHEMA.FILES : To create undo tablespaces in a path relative to the data directory, set the  innodb_undo_directory variable to the relative path, and specify the file name only when creating an undo tablespace. The  InnoDB  recovery process requires that undo tablespace files reside in known directories. Undo tablespace files must be discovered and opened before redo recovery and before other data files are opened to permit uncommitted transactions and data dictionary changes to be rolled back. An undo tablespace not found before recovery cannot be used, which can lead to database inconsistencies. An error message is reported at startup if an undo tablespace known to the data dictionary is not found. The known directory requirement also supports undo tablespace portability. See Moving Undo Tablespaces. If the undo tablespace file name does not include a path, the undo tablespace is created in the directory defined by the  innodb_undo_directory  variable. If that variable is undefined, the undo tablespace is created in the data directory. At startup, directories defined by the  innodb_directories  variable are scanned for undo tablespace files. (The scan also traverses subdirectories.) Directories defined by the  innodb_data_home_dir , innodb_undo_directory , and  datadir  variables are automatically appended to the innodb_directories  value regardless of whether the  innodb_directories  variable is defined explicitly. An undo tablespace can therefore reside in paths defined by any of those variables. In a replication environment, the source and each replica must have its own undo tablespace file directory. Replicating the creation of an undo tablespace file to a common directory would cause a file name conflict. The undo tablespace file name must have an  .ibu  extension. It is not permitted to specify a relative path when defining the undo tablespace file name. A fully qualified path is permitted, but the path must be known to  InnoDB . Known paths are those defined by the  innodb_directories  variable. Unique undo tablespace file names are recommended to avoid potential file name conflicts when moving or cloning data. Note Note Note