本文详细介绍了Oracle数据库中MEMORY_TARGET参数的作用及其配置方法。MEMORY_TARGET参数用于指定Oracle系统可用内存总量，数据库会根据该值自动调整SGA和PGA的大小。文章还解释了MEMORY_MAX_TARGET参数与MEMORY_TARGET的关系，并说明了如何通过ALTER SYSTEM命令动态调整MEMORY_TARGET。
MEMORY_TARGET
| Property | Description |
|---|---|
| Parameter type | Big integer |
| Syntax | MEMORY_TARGET = integer [K | M | G] |
| Default value | 0 (SGA autotuning is disabled for DEFERRED mode autotuning requests, but allowed for IMMEDIATE mode autotuning requests) |
| Modifiable | ALTER SYSTEM |
| Range of values | 152 MB to MEMORY_MAX_TARGET |
| Basic | No |
MEMORY_TARGET specifies the Oracle system-wide usable memory. The database tunes memory to the MEMORY_TARGET value, reducing or enlarging the SGA and PGA as needed.
In a text-based initialization parameter file, if you omit MEMORY_MAX_TARGET and include a value for MEMORY_TARGET, then the database automatically sets MEMORY_MAX_TARGET to the value of MEMORY_TARGET. If you omit the line for MEMORY_TARGET and include a value for MEMORY_MAX_TARGET, the MEMORY_TARGET parameter defaults to zero. After startup, you can then dynamically change MEMORY_TARGET to a nonzero value, provided that it does not exceed the value of MEMORY_MAX_TARGET.
Total memory usage can grow beyond the value of MEMORY_TARGET. For example, memory is allocated to PL/SQL tables and varrays regardless of the value of MEMORY_TARGET as long as memory is available at the operating system level.
In the Default value field, IMMEDIATE mode autotuning requests are necessary to avoid ORA-04031 errors. The DEFERRED and IMMEDIATE modes are reflected in the OPER_MODE column of the V$MEMORY_RESIZE_OPS view.
Note:
The default value ofSGA_MAX_SIZE depends on the values of
MEMORY_TARGET and
MEMORY_MAX_TARGET.
扫一扫
被折叠的 条评论
为什么被折叠?
到【灌水乐园】发言
