scope=memory scope=spfile scope=both 动态修改

scope=memory;---直接修改内存中的值

scope=spfile;---只改的磁盘上的参数，没有更改内存

scope=both;--同时修改内存和磁盘

ALTER SYSTEM 中 SCOPE=SPFILE/MEMORY/BOTH 的区别：

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.

（此更改写入初始化参数文件，更改将在下次启动时生效。动态参数与静态参数都一样可以。也是静态参数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.

（只在内存上修改，立即生效，但重启后将不再生效，因为并没有写入到初始化参数文件。只适用于动态参数，静态参数则不允许。）

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.

（既写入到初始化参数文件，也在内存上修改，立即生效。同样也只适用于动态参数，静态参数则不允许。）

动态修改：

举例：alter system set db_flashback_retention_target=2000；

SQL> alter system set db_flashback_retention_target=2000;


System altered.

可以动态修改。

scope参数说明:

静态参数 必须指定scope

动态参数issys_modifiable为IMMEDIATE不加scope默认的是 both

动态参数issys_modifiable为DEFERRED的必须加上scope=spfile或者加上derferred