InnoDB System Variables dynamic adjustment helps the thread scheduling mechanism to work smoothly during times when the system is lightly loaded or when it is operating near full capacity. For more information, see Section 15.8.4, “Configuring Thread Concurrency for InnoDB” . Used to define an alternate directory for temporary sort files created during online  ALTER TABLE operations that rebuild the table. Online  ALTER TABLE  operations that rebuild the table also create an  intermediate  table file in the same directory as the original table. The  innodb_tmpdir  option is not applicable to intermediate table files. A valid value is any directory path other than the MySQL data directory path. If the value is NULL (the default), temporary files are created MySQL temporary directory ( $TMPDIR  on Unix,  %TEMP%  on Windows, or the directory specified by the  --tmpdir  configuration option). If a directory is specified, existence of the directory and permissions are only checked when  innodb_tmpdir  is configured using a  SET  statement. If a symlink is provided in a directory string, the symlink is resolved and stored as an absolute path. The path should not exceed 512 bytes. An online  ALTER TABLE  operation reports an error if  innodb_tmpdir  is set to an invalid directory.  innodb_tmpdir  overrides the MySQL  tmpdir setting but only for online  ALTER TABLE  operations. The  FILE  privilege is required to configure  innodb_tmpdir . The  innodb_tmpdir  option was introduced to help avoid overflowing a temporary file directory located on a  tmpfs  file system. Such overflows could occur as a result of large temporary sort files created during online  ALTER TABLE  operations that rebuild the table. In replication environments, only consider replicating the  innodb_tmpdir  setting if all servers have the same operating system environment. Otherwise, replicating the  innodb_tmpdir  setting could result in a replication failure when running online  ALTER TABLE  operations that rebuild the table. If server operating environments differ, it is recommended that you configure  innodb_tmpdir  on each server individually. For more information, see Section 15.12.3, “Online DDL Space Requirements” . For information about online  ALTER TABLE  operations, see Section 15.12, “InnoDB and Online DDL” . • innodb_trx_purge_view_update_only_debug 3293 Command-Line Format --innodb-trx-purge-view-update-only- debug[={OFF|ON}] System Variable innodb_trx_purge_view_update_only_debug Scope Global Dynamic Yes Command-Line Format --innodb-tmpdir=dir_name System Variable innodb_tmpdir Scope Global, Session Dynamic Yes SET_VAR  Hint Applies No Type Directory name Default Value NULL • innodb_tmpdir