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).

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_COMPATIBLE initialization parameter must be set to FALSE at the CDB level (in the root of the CDB).

• The MEMORY_TARGET initialization parameter must not be set at the CDB level.

• A value for SGA_TARGET must be set at the CDB level.

  If SGA_TARGET is not set at the CDB level, then setting SGA_MIN_SIZE in a PDB has no effect. You will not receive an error message, and the PDB’s SGA_MIN_SIZE value will not be enforced.

• You must set the SGA_MIN_SIZE value 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_TARGET in the PDB

  • In a PDB, to a value that is less than or equal to 50% of the value of SGA_TARGET at the CDB level

  • In a PDB, to a value that is less than the value of SGA_MAX_SIZE at the CDB level

  • Across all the open PDBs in a CDB, the sum of SGA_MIN_SIZE values must be less than or equal to 50% of the managed SGA total at the CDB level. Managed SGA is DB_CACHE_SIZE plus SHARED_POOL_SIZE.

  When you set SGA_MIN_SIZE in 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