在Oracle中，從9i開始引入了spfile，也就是服務 器端初始化參數，有很多是可以支持在線修改的，也就是修改會馬上生效，詳細內容看下面的說明：

The ISSYS_MODIFIABLE column in V$PARAMETER tells us whether the parameters are static or dynamic. Static parameters require the instance to be restarted while dynamic parameters can take effect immediately upon being changed.

SQL> select distinct issys_modifiable from v$parameter;
 
ISSYS_MODIFIABLE
---------------------------
DEFERRED
FALSE
IMMEDIATE

If the ISSYS_MODIFIABLE value is set to FALSE for a parameter, it means that the parameter cannot change its value in the lifetime of the instance; the database needs to be restarted for changes to take effect. A parameter set to IMMEDATE value means that it is dynamic and can be set to change the present active instance as well as future database restarts. A parameter set to DEFERRED is also dynamic, but changes only affect subsequent sessions, currently active sessions will not be affected and retain the old parameter value.