High parallel_max_servers

LHDZ-BJ

学习了。

daizyflower

netbanker

Yong Huang 发表于 2013-3-5 07:47
Parallel_automatic_tuning is deprecated even in 10gR1:
http://docs.oracle.com/cd/B12037_01/server.1 ...

这个：　PARALLEL_ADAPTIVE_MULTI_USER

rocyang

d

sundog315

虽然我很支持，但目前为止，还没有发现设置什么值是一个合理的值，也没明白为什么Oralce计算的值如此之高。

因此，在可使用并行的数据库环境里，大部分情况下设置CPU_COUNT=物理核数，PARALLEL_THREADS_PER_CPU=1，关闭CPU的超线程。

sundog315

对了，昨天在看一个OLAP的文档，提到了这个

OLAP Performance Tuning [ID 413648.1]

Change PARALLEL_MAX_SERVERS to the number of processors less 1 so that AWs use as many parallel slaves as available (normally this is set too high by default install)

processors-1

Yong Huang

Thanks for that reference. Setting it to "the number of processors less 1" makes good sense. And "normally this is set too high by default install" is a clear snap on the face of whoever at Oracle makes the fancy imagination in his ivory tower.

That article is about OLAP. I've always wondered whether I need to use that kind of stuff, when I see it as an option in database installation, and see the parameter olap_page_pool_size or those undocumented ones. Dbms_aw package is something I've never bothered to check. Not sure when I need it. According to
http://docs.oracle.com/cd/E11882 ... dml_app_dbms_aw.htm
it's for analytic workspace. But anyway, I assume the suggestion in the article is not necessarily specific to OLAP or AW.

When you say "关闭CPU的超线程", you mean disable it at OS level? Is there any specific reason you want to disable CPU hyperthreading? Or you just mean setting PARALLEL_THREADS_PER_CPU=1 in Oracle only?

wolfop

Only before nehalaem CPU need disable HT. After xeon 5500, 75xx, ENABLE HT is a good idea.

Yong Huang

Nehalem CPU hyperthreading is buggy and so should be disabled? I can't find such suggestion on MOS (My Oracle Support).

ly215197

sundog315 发表于 2013-3-22 11:09
对了，昨天在看一个OLAP的文档，提到了这个

OLAP Performance Tuning

在吗？