https://blog.csdn.net/dba_monkey/article/details/60141467

scope=memory scope=spfile scope=both 動態修改
scope=memory;---直接修改記憶體中的值
scope=spfile;---只改的磁碟上的引數，沒有更改記憶體
scope=both;--同時修改記憶體和磁碟

ALTER SYSTEM 中 SCOPE=SPFILE/MEMORY/BOTH 的區別：
SCOPE = SPFILE
 The change is applied in theserverparameter file only. The effect is as follows:
■ For dynamic parameters, the change is effective at the next startup and is persistent.
■ For static parameters, the behavior. is the same as for dynamic parameters. This is the only SCOPE specification allowed for static parameters.
（此更改寫入初始化引數檔案，更改將在下次啟動時生效。動態引數與靜態引數都一樣可以。也是靜態引數唯一可以使用的方式。）

SCOPE = MEMORY
The change is applied in memory only. The effect is as follows:
■ For dynamic parameters, the effect is immediate, but it is not persistent because the server parameter file is not updated.
■ For static parameters, this specification is not allowed.
（只在記憶體上修改，立即生效，但重啟後將不再生效，因為並沒有寫入到初始化引數檔案。只適用於動態引數，靜態引數則不允許。）

SCOPE = BOTH
The change is applied in both the server parameter file and memory. The effect is as follows:
■ For dynamic parameters, the effect is immediate and persistent.
■ For static parameters, this specification is not allowed.
（既寫入到初始化引數檔案，也在記憶體上修改，立即生效。同樣也只適用於動態引數，靜態引數則不允許。）