Oracle 参数 READ_ONLY_OPEN_DELAYED 官方解释，作用，如何配置最优化建议
本站中文解释
READ_ONLY_OPEN_DELAYED参数指定对于只读表空间的文件打开方式，当为TRUE时表示延迟打开只读表空间的文件，即当磁盘空间不足时，文件才会被使用，为FALSE时表示在实例启动时就打开只读表空间的文件，所有文件都会立即被打开，此参数可以被动态调整，默认值为FALSE。
正确设置READ_ONLY_OPEN_DELAYED参数：
对于只读表空间，设置READ_ONLY_OPEN_DELAYED参数为TRUE可以延迟文件的打开，可以减少磁盘空间的消耗，从而提高系统的性能。可以通过以下方法设置：
ALTER SYSTEM SET READ_ONLY_OPEN_DELAYED = TRUE SCOPE = SPFILE;
但是如果数据库内部存在复杂的应用程序，可能需要立即操作只读表空间，此时应当关闭此参数：
ALTER SYSTEM SET READ_ONLY_OPEN_DELAYED = FALSE SCOPE = SPFILE;
官方英文解释
READ_ONLY_OPEN_DELAYED determines when datafiles in read-only tablespaces are accessed.
| Property | Description |
|---|---|
|
Parameter type |
Boolean |
|
Default value |
|
|
Modifiable |
No |
|
Modifiable in a PDB |
No |
|
Range of values |
|
|
Basic |
No |
Values
-
trueThe datafiles are accessed for the first time only when an attempt is made to read data stored within them.
-
falseThe datafiles are accessed at database open time.
You can use this parameter to speed up some operations (primarily opening the database) for very large databases when substantial portions of the database are stored in read-only tablespaces. Consider setting this parameter to true for such databases, especially if portions of the read-only data are stored on slow-access devices or hierarchical storage.
See Also:
Oracle Database
Administrator’s Guide for information on the consequences of delaying access of datafiles in read-only tablespaces
