當使用spfile時，不用重新開機就能生效的初始化參數，可以通過v$parameter.ISSYS_MODIFIABLE字段來判斷。
v$parameter.ISSYS_MODIFIABLE參數
Indicates whether the parameter can be changed with ALTER SYSTEM and when the change takes effect:
IMMEDIATE - Parameter can be changed with ALTER SYSTEM regardless of the type of parameter file used to start the instance. The change takes effect immediately.
DEFERRED - Parameter can be changed with ALTER SYSTEM regardless of the type of parameter file used to start the instance. The change takes effect in subsequent sessions.
FALSE - Parameter cannot be changed with ALTER SYSTEM unless a server parameter file was used to start the instance. The change takes effect in subsequent instances.
[email protected]>select distinct ISSYS_MODIFIABLE from v$parameter;
ISSYS_MODIFIABLE
------------------------------
IMMEDIATE
FALSE
DEFERRED
[email protected]>select name,ISSYS_MODIFIABLE from v$parameter where name='statistics_level';
NAME ISSYS_MODIFIABLE
------------------------------ ------------------------------
statistics_level IMMEDIATE
[email protected]>select name,ISSYS_MODIFIABLE from v$parameter where name='processes';
NAME ISSYS_MODIFIABLE
------------------------------ ------------------------------
processes FALSE
[email protected]>select name,ISSYS_MODIFIABLE from v$parameter where name='sort_area_size';
NAME ISSYS_MODIFIABLE
------------------------------ ------------------------------
sort_area_size DEFERRED
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