结论：

1,events可以动态修改
2,event必须重启库方可生效

测试

SQL> show parameter event


NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
event                                string
SQL> alter system set event='10046 trace name context forever,level 12';
alter system set event='10046 trace name context forever,level 12'
                 *
ERROR at line 1:
ORA-02095: specified initialization parameter cannot be modified




SQL> alter system set event='10046 trace name context forever,level 12' scope=spfile;


System altered.


SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup
ORA-32004: obsolete and/or deprecated parameter(s) specified
ORACLE instance started.


Total System Global Area 1157627904 bytes
Fixed Size                  2095800 bytes
Variable Size             402654536 bytes
Database Buffers          721420288 bytes
Redo Buffers               31457280 bytes
Database mounted.
Database opened.
SQL> show parameter event


NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
event                                string      10046 trace name context forev
                                                 er,level 12
SQL> 


SQL> alter system set event='' scope=spfile;


System altered.


SQL> alter system set events='10046 trace name context forever,level 12';


System altered.