s indicated below. 数据库范围使用“*”，实例范围使用“SID.”
*.OPEN_CURSORS=400 # For database-wide setting
RACDB1.OPEN_CURSORS=800# For RACDB1 instance
Note that even though open_cursors is set at 400 for all instances in the first entry, the value of 800 remains in effect for the SID 'RACDB1'. ---相当于就近原则，优先级不一样
Some initialization parameters are dynamic since they can be modified using the ALTER SESSION or ALTER SYSTEM statement while an instance is running. Use the following syntax to dynamically alter
initialization parameters:
ALTER SESSION SET parameter_name = value
ALTER SYSTEM SET parameter_name = value [DEFERRED]
Use the SET clause of the ALTER SYSTEM statement to set or change initialization parameter values. Additionally, the SCOPE clause specifies the scope of a change as described below:
SCOPE = SPFILE ----对所有的动态参数和静态参数，使用这个语句都是在下次重启之后生效
(For both static and dynamic parameters, changes are recorded in the spfile, to be given effect in the next restart.)
SCOPE = MEMORY ---- 对于动态参数进行调整，下次重启失效
(For dynamic parameters, changes are applied in memory only. No static parameter change is allowed.)
SCOPE = BOTH ---对于动态参数有效，当前和重启均生效，可以指定DEFERRED参数，延迟生效
For dynamic parameters, the change is applied in both the server parameter file and memory. No static parameter change is allowed.)
For dynamic parameters, we can also specify the DEFERRED keyword. When specified, the change is effective only for future sessions.
HERE ARE A FEW EXAMPLES 一些例子
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The following statement affects all instances. However, the values are only effective for the current instances, they are not written to binary SPFILE.
ALTER SYSTEM SET OPEN_CURSORS=500 SID='*' SCOPE=MEMORY;
The next statement resets the value for the instance 'RACDB1'.
At this point, the database-wide setting becomes effective for SID of RACDB1.
ALTER SYSTEM RESET OPEN_CURSORS SCOPE=SPFILE sid='RACDB1';
To reset a parameter to its default value throughout the cluster database, use the command:
ALTER SYSTEM RESET OPEN_CURSORS SCOPE=SPFILE sid='*';
CREATING A SERVER PARAMETER FILE ---创建一个参数文件
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The server parameter file is initially created from a text initialization parameter file (init.ora).
It must be created prior to its use in the STARTUP command.
The create SPFILE statement is used to create a server parameter file.
The following example creates a server parameter file from an initialization parameter file.
CREATE SPFILE FROM PFILE='/u01/oracle/product/920/dbs/initRAC1.ora';
Below is another example that illustrates creating a server parameter file and supplying a name.
CREATE SPFILE='/u01/oracle/product/920/dbs/racdb_spfile.ora'
FROM PFILE='/u01/oracle/product/920/dbs/init.ora';
EXPORTING THE SERVER PARAMETER FILE --- 导出参数文件
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We can export the server parameter file to create a traditional text initialization parameter file.
This would be useful for:（作用）
1) Creating backups of the server parameter file. --备份
2) For diagnostic purposes to list all of the parameter values currently used by an instance. 诊断
3) Modifying the server parameter file by first exporting it, editing the output file, and then recreating it. 外部编辑
The following example creates a text initialization parameter file from the server parameter file:
CREATE PFILE FROM SPFILE;
The example below creates a text initialization parameter file from a server parameter file, where the names of the files are specified:
CREATE PFILE='/u01/oracle/pr |