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(A possible answer.)

Setting a global variable (anyone, not just this one), does not take effect immediately:


If you set it in my.cnf (etc), it would take effect until after a restart
If it is set globally (SET GLOBAL @@... ), it won't take effect until someone logs in -- he then gets that setting.  (Caveat: Some globals have no "session" counterpart, so they don't act this way.)
If you set it in your session, it does not apply to anyone else.


If this does not answer the question, please show us precisely how you set it.  And provide SELECT @@version;