Oracle 参数 SGA_MAX_SIZE 官方解释，作用，如何配置最优化建议
本站中文解释
SGA_MAX_SIZE参数用于指定SGA的最大大小，SGA的最大大小由当前的内存限制和系统的类型决定，这个参数在安装后就被设置好了，可通过查询V$SGA_DYNAMIC_SIZE视图来查看，也可以修改该参数，但需要注意：修改该参数一定要改得大于所有SGA组件当前大小，否则会报错无法启动数据库；而且这个参数只能在instance shutdown的状态下修改的，且在执行alter system的时候，应该带上参数scope（影响范围），如：alter system set sga_max_size =xxG scope = memonly。
官方英文解释
SGA_MAX_SIZE specifies the maximum size of the SGA for the lifetime of the instance.
| Property | Description |
|---|---|
|
Parameter type |
Big integer |
|
Syntax |
|
|
Default value |
Initial size of SGA at startup, dependent on the sizes of different pools in the SGA, such as buffer cache, shared pool, large pool, and so on. |
|
Modifiable |
No |
|
Modifiable in a PDB |
No |
|
Range of values |
0 to operating system-dependent |
On 64-bit platforms and non-Windows 32-bit platforms, when either MEMORY_TARGET or MEMORY_MAX_TARGET is specified, the default value of SGA_MAX_SIZE is set to the larger of the two parameters. This causes more address space to be reserved for expansion of the SGA.
On Windows 32-bit platforms, the default value of SGA_MAX_SIZE is the largest of the following values:
-
60% of
MEMORY_TARGET, if specified -
60% of
MEMORY_MAX_TARGET, if specified -
25% of the total available virtual address space
See Also:
Oracle Database
Performance Tuning Guide for more information about this parameter
