Oracle 参数 PARALLEL_MIN_DEGREE 官方解释，作用，如何配置最优化建议
本站中文解释
PARALLEL_MIN_DEGREE参数是控制Oracle采用并行查询时进程数的最少的参数。默认的时候，如果要并行查询一个表，Oracle会自动分配最少的进程数，但是可以通过设置PARALLEL_MIN_DEGREE参数来控制这个最少的进程数，而不让Oracle来决定。
PARALLEL_MIN_DEGREE只能够使用在支持Parallel Query的场合。否则设置也是没有用的。 如果要设置该参数，可以使用如下SQL语句：
ALTER SYSTEM SET PARALLEL_MIN_DEGREE = ;
是希望启用的最小并行查询参数， 默认为2，该参数最大值为 CPU_COUNT * 2;
PARALLEL_MIN_DEGREE设置参数过大也会导致性能下降，因此要考虑清楚后再设置。
官方英文解释
PARALLEL_MIN_DEGREE controls the minimum degree of parallelism computed by automatic degree of parallelism.
| Property | Description |
|---|---|
|
Parameter type |
String |
|
Syntax |
|
|
Default value |
1 |
|
Modifiable |
|
|
Modifiable in a PDB |
Yes |
|
Basic |
No |
|
Oracle RAC |
A different value can be set on different instances. |
The value of PARALLEL_MIN_DEGREE is either a number that corresponds to the lower bound on the degree of parallelism computed by automatic degree of parallelism, or the string value CPU, which is computed by the function CPU_COUNT * PARALLEL_THREADS_PER_CPU.
The default value of PARALLEL_MIN_DEGREE is 1.
Note:
PARALLEL_MIN_DEGREE has no impact in either of these cases:
-
When the value of
PARALLEL_MIN_DEGREEis greater than the value ofCPU_COUNT -
When the object is Oracle-owned, such as a dictionary table or view created on a dictionary table
See Also:
-
“PARALLEL_DEGREE_LIMIT”
-
Oracle Database VLDB and
Partitioning Guide for information about how the optimizer automatically determines the degree of parallelism for a statement
