The listing of Dynamic System Variables on the MySQL Reference Manual's page is supposed to show those variables you can change on-the-fly."innodb_data_home_dir" is listed there as a dynamic variable, but it is not one, and trying to change it on-the-fly doesn't work: mysql> set global innodb_data_home_dir="/data/mysql/data";ERROR 1193 (HY000): Unknown system variable 'innodb_data_home_

Today's contradiction:MySQL has server variables named "new" and "old".The "new" variable can be set per-session and globally, and is dynamic. The "old" variable is not dynamic, and only global in scope. Both default to FALSE in MySQL 5.1.According to the manual, the "new" variable:was used in MySQL 4.0 to turn on some 4.1