Oracle教程 2023-03-24

Oracle 参数 INMEMORY_SIZE 官方解释，作用，如何配置最优化建议

本站中文解释

INMEMORY_SIZE参数控制In-Memory表所需要使用的内存大小，它可以为In-Memory表级别或整个实例设置，也可以设置为两者的组合。

当然，INMEMORY_SIZE只能设置大于或等于有效表的大小的内存量。由于In-Memory表的读写性能受到内存大小的约束，因此，设置足够大的INMEMORY_SIZE是实现最佳性能的关键。

要设置INMEMORY_SIZE，请使用下面的语法：

— 设置整个实例的INMEMORY_SIZE：

ALTER SYSTEM SET INMEMORY_SIZE= SCOPE=SPFILE;

— 设置表级别的INMEMORY_SIZE：

ALTER TABLE

INMEMORY PRIORITY HIGH MEMCOMPRESS FOR QUERY HIGH INMEMORY_SIZE ;

官方英文解释

INMEMORY_SIZE sets the size of the In-Memory Area, which contains the IM Column Store (IM column store) on a database instance.

Property	Description
Parameter type	Big integer
Syntax	`INMEMORY_SIZE =` `integer` `[K \| M \| G]`
Default value	`0`
Modifiable	`ALTER SYSTEM`
Modifiable in a PDB	Yes
Range of values	0 to the amount of memory left in the SGA after other allocations
Basic	No
Oracle RAC	All instances should use the same value.

The default value is 0, which means that the IM column store is not used.

The database must be restarted after setting this parameter to enable the IM column store.

The minimum size to which this parameter can be set is 100 MB.

Typically this parameter should be set to at least the size needed to accommodate all the tables that will use the IM column store. It can be set higher to allow for growth of those tables or to accommodate other tables that will use the IM column store in the future.

This parameter can also be set per PDB to limit the maximum size of the IM column store for that PDB. Note that the sum of the PDB values do not have to equal the CDB value, and the sum of the PDB values may even be greater than the CDB value.

Unless this parameter is specifically set on a PDB, each PDB inherits the CDB value, which means they can use all of the available IM column store.

The value specified for this parameter counts toward SGA_TARGET. For example, if you set SGA_TARGET to 10 GB and you set INMEMORY_SIZE to 2 GB, then 20% of the SGA_TARGET setting is allocated to the In-Memory Area.

Unlike other SGA components such as the buffer cache and shared pool, the In-Memory Area size is not controlled by automatic memory management. The database does not automatically shrink the In-Memory Area when the buffer cache or shared pool requires more memory, or increase the In-Memory Area when it runs out of space. You can only increase the size of the In-Memory Area by manually adjusting the INMEMORY_SIZE initialization parameter.

In-Memory Dynamic Scans require the Resource Manager. Therefore, the Resource Manager is automatically enabled when you change the value of INMEMORY_SIZE from 0 to a non-zero value. No specific resource plan is required.

Database In-Memory Base Level allows a maximum of 16 GB for the size of the In-Memory area. Therefore, if Database In-Memory Base Level is enabled (the value of the INMEMORY_FORCE initialization parameter is set to BASE_LEVEL), then the value of INMEMORY_SIZE cannot exceed 16 GB for a CDB. In an Oracle RAC environment, the value of INMEMORY_SIZE is limited to 16 GB for each instance.

本站中文解释

官方英文解释

相关推荐