Oracle 参数 DBNEST_ENABLE 官方解释，作用，如何配置最优化建议
本站中文解释
DBNEST_ENABLE是Oracle数据库的参数，用于决定是否启用复杂SQL嵌套查询。设置此参数为TRUE时，Oracle会使用复杂sql嵌套查询，从而获得更好的性能。
设置此参数的正确方式是：首先，执行SQL语句，将DBNEST_ENABLE设置为TRUE：
alter system set dbnest_enable=true;
其次，使用ALTER SYSTEM SET 命令将DBNEST_ENABLE参数设置为FALSE：
alter system set dbnest_enable=false;
最后，在刷新之后，可以使用SHOW PARAMETERS dbnest_enable命令来查看DBNEST_ENABLE参数是否已经设置为TRUE或FALSE：
show parameters dbnest_enable
如果查看到输出为dbnest_enable=true，则表示DBNEST_ENABLE参数已经设置为TRUE。
官方英文解释
DBNEST_ENABLE allows you to enable or disable dbNest.
Note:
This parameter is applicable only on Linux systems.
| Property | Description |
|---|---|
|
Parameter type |
String |
|
Syntax |
|
|
Default value |
|
|
Modifiable |
No |
|
Modifiable in a PDB |
No |
|
Basic |
No |
|
Oracle RAC |
All instances should use the same value. |
DbNest provides operating system resource isolation and management, file system isolation, and secure computing for PDBs. The infrastructure is implemented as a Linux-specific package that provides hierarchical containers, called nests. A CDB resides within a single parent nest, while PDBs reside within the individual child nests created within the parent. The isolation and resource management properties of a nest are separate. A full nest includes both isolation and resource management. Alternatively, you can configure a partial nest that includes only resource management.
You can set the following values for this parameter:
-
NONE: Disables dbNest. This is the default value. -
CDB_RESOURCE_PDB_ALL: Enables a resource management-only nest for the CDB and a full nest for each PDB.
Note:
This parameter is available starting with Oracle Database 21c.
See Also:
Oracle Multitenant
Administrator’s Guide for information on securing and isolating resources using dbNest
