Oracle引數修改後的生效判定

當使用spfile時，不用重啟就能生效的初始化引數，可以透過v$parameter.ISSYS_MODIFIABLE欄位來判斷。

v$parameter.ISSYS_MODIFIABLE引數
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.

sys@RACDB>select distinct ISSYS_MODIFIABLE from v$parameter;

ISSYS_MODIFIABLE
------------------------------
IMMEDIATE
FALSE
DEFERRED

ys@RACDB>select name,ISSYS_MODIFIABLE from v$parameter where name='statistics_level';

NAME                   ISSYS_MODIFIABLE
------------------------------ ------------------------------
statistics_level           IMMEDIATE

sys@RACDB>select name,ISSYS_MODIFIABLE from v$parameter where name='processes';

NAME                   ISSYS_MODIFIABLE
------------------------------ ------------------------------
processes               FALSE

sys@RACDB>select name,ISSYS_MODIFIABLE from v$parameter where name='sort_area_size';

NAME                   ISSYS_MODIFIABLE
------------------------------ ------------------------------
sort_area_size               DEFERRED