To set correct system variable values is the essential step to
get the correct server behavior against the workload.
In MySQL, we have many System variables that can be changed at runtime, and most of them can be set at the session or global level.
To change the value of a system variable at the global level in the past, users needed to have SUPER privileges. Once the system variable value is modified as global, the server will change this behavior for the session, and obviously as global scope.
For instance, one of the most commonly adjusted variables is probably max_connections.
If you have max_connection=100 in your my.cnf or as the default value, and during the day as DBA you notice that it is not enough, it is easy just to add new connections on the fly with the command:
SET GLOBAL …[Read more]