Oracle 参数 SGA_MIN_SIZE 官方解释，作用，如何配置最优化建议
本站中文解释
、SGA_TARGET
SGA_MIN_SIZE：
SGA_MIN_SIZE参数指定操作系统允许Oracle数据库使用多少内存空间用于初始化系统全局区（System Global Area, SGA），参数的默认值是0，表示空间未被限定，它的值同时也等于SGA_TARGET的值；
SGA_TARGET：
SGA_TARGET参数指定操作系统允许Oracle数据库为SGA分配多少内存空间，参数的默认值是0，表示动态SGA技术没有被启用，此时两个参数的值是一致的；如果你不想受到操作系统资源占用方面的限制，你可以将SGA_TARGET设置为0，但是这种情况可能会使Oracle占用更多的资源，从而影响其它应用程序的运行。
正确设置：
需要根据实际情况确定SGA_MIN_SIZE和SGA_TARGET的适当值，在定义之前，应该考虑当前的负载，包括操作和管理的数据，要使系统正常运行，SGA_MIN_SIZE和SGA_TARGET的值必须大于0，且两者的值越大，读取数据的效率越高。
官方英文解释
SGA_MIN_SIZE indicates a possible minimum value for SGA usage of a pluggable database (PDB).| Property | Description |
|---|---|
|
Parameter type |
Big integer |
|
Syntax |
|
|
Default value |
|
|
Modifiable |
|
|
Modifiable in a PDB |
Yes |
|
Range of values |
0 to 50% of |
|
Basic |
No |
|
Oracle RAC |
The same value must be used for all instances. |
Setting this parameter at the CDB level has no effect.
Note:
To be able to use Resource Manager in a CDB to control the amount of memory each PDB can use:
-
The
NONCDB_COMPATIBLEinitialization parameter must be set toFALSEat the CDB level (in the root of the CDB). -
The
MEMORY_TARGETinitialization parameter must not be set at the CDB level. -
A value for
SGA_TARGETmust be set at the CDB level.If
SGA_TARGETis not set at the CDB level, then settingSGA_MIN_SIZEin a PDB has no effect. You will not receive an error message, and the PDB’sSGA_MIN_SIZEvalue will not be enforced. -
You must set the
SGA_MIN_SIZEvalue to a value that meets these requirements:-
In a PDB, to a value that is less than or equal to 50% of the value of
SGA_TARGETin the PDB -
In a PDB, to a value that is less than or equal to 50% of the value of
SGA_TARGETat the CDB level -
In a PDB, to a value that is less than the value of
SGA_MAX_SIZEat the CDB level -
Across all the open PDBs in a CDB, the sum of
SGA_MIN_SIZEvalues must be less than or equal to 50% of the managed SGA total at the CDB level. Managed SGA isDB_CACHE_SIZEplusSHARED_POOL_SIZE.
When you set
SGA_MIN_SIZEin a PDB to a value that does not meet these requirements, you receive an error. -
See Also:
Oracle Multitenant
Administrator’s Guide for more information about the initialization parameters that control the memory usage of PDBs
