如何查询一个 隐含参数的值?
直接用 show parameter <parameter> 是不行的。
可以用如下的语句：
例如要查隐含参数 _parallel_cluster_cache_policy 的值：
select a.ksppinm "Parameter",a.KSPPDESC "Description",b.ksppstvl "Value" from x$ksppi a,x$ksppcv b where a.indx = b.indx and a.ksppinm like ‘%_parallel_cluster_cache_policy%‘;
结果的例子：
SQL> select a.ksppinm "Parameter"
2 ,a.KSPPDESC "Description"
3 ,b.ksppstvl "Value"
4 from x$ksppi a
5 ,x$ksppcv b
6 where a.indx = b.indx
7 and a.ksppinm like ‘%_parallel_cluster_cache_policy%‘;
Parameter
--------------------------------------------------------------------------------
Description
--------------------------------------------------------------------------------
Value
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_parallel_cluster_cache_policy
policy used for parallel execution on cluster(ADAPTIVE/CACHED)
CACHED
原文：https://www.cnblogs.com/gaojian/p/14636648.html