OCP-1Z0-053-V12.02-80题

最新推荐文章于 2017-07-04 11:15:15 发布

Riveore

最新推荐文章于 2017-07-04 11:15:15 发布

阅读量8.2k

点赞数

CC 4.0 BY-SA版权

分类专栏： OCP-1Z0-053 OCP11g解析

本文链接：https://blog.youkuaiyun.com/rlhua/article/details/14109335

OCP11g解析同时被 2 个专栏收录

870 篇文章

订阅专栏

OCP-1Z0-053

796 篇文章

订阅专栏

本文探讨了SQL配置文件的创建过程及如何被查询优化器使用。当接受一个配置文件时，数据库会将其持久化存储在数据字典中。如果针对已建立配置文件的语句发出指令，则查询优化器将结合环境和SQL配置文件来构建调优计划。

80.Which two statements regarding a SQL profile are true? (Choose two.)

A. It is built by Automatic Tuning Optimizer.

B. It cannot be stored persistently in the data dictionary.

C. It can be used by the query optimizer automatically.

D. It can be created manually by using the CREATE PROFILE command.

Answer: AC

答案解析：

参考： http://docs.oracle.com/cd/E11882_01/server.112/e41573/sql_tune.htm#PFGRF94873

SQL Profile Creation

When you accept a profile, the database creates the profile and stores it persistently in the data dictionary. If a user issues a statement for which a profile has been built, then the query optimizer (in normal mode) uses both the environment and the SQL profile to build a well-tuned plan.

As a rule of thumb, accept a SQL profile recommended by SQL Tuning Advisor. If both an index and a SQL profile are recommended, then either use both or use the SQL profile only. If you create an index, then the optimizer may need the profile to pick the new index.

In some situations, SQL Tuning Advisor may find an improved serial plan in addition to an even better parallel plan. In this case, the advisor recommends both a standard and a parallel SQL profile, enabling you to choose between the best serial and best parallel plan for the statement. Accept a parallel plan only if the increase in response time is worth the decrease in throughput