阐释如何解释联邦查询执行计划。
Illustrates how to interpret a federated query execution plan.
步骤2.1：检查查询执行计划。
先从了解查询执行计划开始。
This starts with understanding your queries' execution plans.
影响查询执行计划的主要数据库配置参数设置如下
The main database configuration parameter settings that affect the query execution plan were set as follows
这使您可以在真正的生产环境中获取查询执行计划。
This makes it possible to get query execution plan in the real production environment. To use this new feature, you need to use the key word AVOID_EXECUTE in SET EXPLAIN ON statement as follows
您可以分析查询执行计划输出，以确定这是否是必需的。
You can analyze the query execution plan output to decide whether or not this is necessary.
这个查询执行计划可以使用db2exfmt工具查看
The query execution plan can be viewed using the db2exfmt tool
根据总体查询执行计划，将随后对数据源执行各个子操作。
According to the overall query execution plan, the sub operations are then applied at the sources.
在研究查询执行计划的问题时，片段解释和片段实绩是非常强大的特性。
Section explains and section actuals are very powerful features to investigate problems with a query execution plan.
该文以丛生树模型为基础，提出了一种片段式查询执行计划。
In this paper, we offer a segmented query executive plan which is based on bushy tree model.
在这一步中，需要挖掘上面所收集的统计数据，并仔细查看查询执行计划。
At this step, you need to dig into the statistics you collected above and take a good look at the query execution plan.
更新统计数据是最重要的管理任务之一，它确保优化器选用最佳的查询执行计划。
Updating statistics is one of the most important administrative tasks that ensure the optimizer picks optimum execution plans for your queries.
关于如何解释FQEP的详细说明可以在“解释联邦查询执行计划”小节中找到。
Detailed instructions on how to interpret a FQEP can be found under the section, "Interpreting Federated Query Execution Plans."
优化器是依靠统计信息来计算可选查询执行计划（QEP）的开销，同时选择出最优的计划。
The optimizer relies on statistics to properly cost alternative query execution plans (QEPs) and choose the most optimal plan.
DB 2 9.5优化器使用两种类型的索引来优化查询，并帮助选择最佳的查询执行计划。
The DB2 9.5 optimizer USES both type of indexes to optimize the queries and help selecting the best plan for query execution.
当评估查询执行计划时，优化器计算并比较每种连接方法的成本，然后选择要使用的最佳方法。
The optimizer calculates and compares the costs of each join method and selects the best one to use when evaluating query execution plans.
这种优化方法大大地缩减了查询执行计划空间，确保了并行查询执行计划的优化性。
This method cuts down query plan search space greatly, thus ensures the quality of parallel query execution plans.
通过内部统计数据，我指的是系统目录中的统计数据，优化器可以确定最低成本的查询执行计划。
By internal statistics, I mean the statistics in the system catalogs that the optimizer USES to determine the lowest-cost query execution plan.
您可以使用VisualExplain或db 2 exfmt的输出来获得查询执行计划。
You can use the output of Visual Explain or db2exfmt to obtain the query execution plan.
统计视图和REOPT都使优化器可以计算出更精确的基数估计，而后选择一个最佳查询执行计划。
Both statistical views and REOPT allow the optimizer to compute a more accurate cardinality estimate and consequently choose an optimal query execution plan.
当我检查的SQL查询执行计划，这似乎是很不一致的方式试图优化这个查询的SQL。
And when I check on the SQL query execution plan, it seems to be pretty inconsistent in how SQL tries to optimize this query.
“动态”意味着查询作为字符串发送给数据库引擎；必须对它进行解析，并生成查询执行计划。
"Dynamic" means that the query is sent into the database engine as a string; it must be parsed and have a query execution plan generated.
本文从索引、提示和查询执行计划等角度来讨论查询优化技巧，希望能给大家带来一些帮助。
This paper discussed the optimized skills of enquiry from the perspectives of index , hints and enquiring executive plan .
当设置了该选项时，查询优化器选择按照PDA的指示将大部分工作下推到数据源的查询执行计划。
When this option is set, the query optimizer chooses the query execution plan that pushes the most work down to the data source as indicated by the PDA component.
因此，我们在这些连接列上添加了索引，从下列查询执行计划中我们可以看到，查询成本减少了很多。
So we added indexes on those joining columns and from the following query execution plan, we can see the query cost is greatly reduced.
对于SELECT查询，远程sql语句中的文本可以在查询执行计划中与SHIP操作符相关的细节中找到。
For SELECT queries, the text of the remote SQL statement can be found in the details associated with the SHIP operator in the query execution plan.
并行查询执行计划的搜索空间里指数级增长，如何高效地裁剪搜索空间是并行查询优化的关键所在。
The search space of parallel query execution plan is exponential complexity. How to prune the search space efficiently is the key problem of parallel query optimization.
从版本9.3开始，该实用程序得到了较好的提高；您可以获取详细的查询执行计划，而不必执行该查询。
From version 9.3 on, there is a nice enhancement of this utility; you can get the detailed query execution plan without ever executing the query.
当应用程序向设备的主机服务器发送一个查询时，处理流程开始。 主机服务器将编译该查询并创建一个优化的查询执行计划。
The action begins when an application sends a query to the appliance host server, which compiles the query and creates an optimized query execution plan.
当应用程序向联邦系统提交一个查询时，联邦服务器识别相关数据源，并生成一个用于获得被请求数据的查询执行计划。
When an application submits a query to the federated system, the federated server identifies the relevant data sources, and develops a query execution plan for obtaining the requested data.
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