How to Enable MySQL Slow Query Log Without Server Restart

Q: I can only set the slow query threshold with the method recommended at http://crazytoon.com/2007/07/23/. Is there anything else needed, such as specifying a filepath?

A: According to the MySQL documentation, the default slow query log file name is host_name-slow.log located in the data directory. If you don't see a log file when running SHOW VARIABLES, it's likely because you're using MySQL version 5.0.77 or earlier. For these versions, use the following command:

SET GLOBAL log_slow_queries = 1;

However, since MySQL 5.1, you can use the following command:

SET GLOBAL slow_query_log = 'ON';

Remember to flush the logs with FLUSH LOGS.