MySQL wait_timeout Variable - GLOBAL vs SESSION

Question

SHOW VARIABLES LIKE \"%wait%\"

Result: 28800

SET @@GLOBAL.wait_timeout=300

SHOW GLOBAL VARIABLES LIKE \"%wait%\"

Result: 300

SHOW SESSION VARIABLES LIKE \"%wait         


        

Answer 1

SHOW SESSION VARIABLES LIKE "wait_timeout"; -- 28800
SHOW GLOBAL VARIABLES LIKE "wait_timeout"; -- 28800

At first, wait_timeout = 28800 which is the default value. To change the session value, you need to set the global variable because the session variable is read-only.

SET @@GLOBAL.wait_timeout=300

After you set the global variable, the session variable automatically grabs the value.

SHOW SESSION VARIABLES LIKE "wait_timeout"; -- 300
SHOW GLOBAL VARIABLES LIKE "wait_timeout"; -- 300

Next time when the server restarts, the session variables will be set to the default value i.e. 28800.

P.S. I m using MySQL 5.6.16