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, most of them can be set at session or at global
scope.
To change the value of a system variable at global level in the
past user need to have SUPER privileges. Once the system variable
value is modified as global, the server will change his 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 default value, and during the day as DBA you notice that the
number of them is not enough, it is easy just to add new
connections on the fly, the command:
SET GLOBAL MAX_CONNECTIONS=500;
Will do the work. But here is the issue. We had changed a GLOBAL
value, that apply to the whole …
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