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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” . 

• innodb_tmpdir 

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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 

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