The optimizer is the heart and soul of DB2.
优化器是 DB2的心脏和灵魂。
When the optimizer can choose a star join plan.
优化器何时可以选择星型连接计划。
The order of indexes is chosen by the optimizer.
索引的顺序由优化器选择。
Now the optimizer should have a good starting point.
现在优化器应该有一个良好的起点。
The choice of the access method is left to the optimizer.
选择访问方法的任务交给优化器来完成。
If the optimizer still reports a bad result, try the following.
如果优化器还报告不好的结果，尝试以下。
Another way to influence the optimizer is to use query directives.
影响优化器的另一种方式就是使用查询命令。
Multiple index scans in the optimizer are another big win for OLTP.
优化器中的多索引扫描是OLTP的另一大赢点。
The optimizer will return the best plan using a cost-based decision.
优化器将通过基于成本的决策返回最佳计划。
You can help the optimizer by providing a reasonable starting point.
你可以帮助优化提供了一个合理的起点。
The optimizer can decide to not use an index even if it could be used.
优化器可以决定不使用索引，即使该索引是可以使用的。
A query access plan similar to the following is chosen by the optimizer.
优化器会选择类似如下所示的查询访问计划。
Therefore the optimizer is aware of the different frequencies of the available models.
因此，优化器清楚各种已有型号出现的不同频率。
The access guideline (any access request) allows the optimizer to choose the access method.
ACCESS准则(任何访问请求)允许优化器选择方法。
This can happen when the optimizer does not have the necessary information at planning time.
如果优化器在计划时没有必要的信息就会造成这种情况。
Examples of the statistics available which help define the data model to the optimizer include.
下面列举了一些统计信息，这些统计信息可以帮助给优化器定义数据模型。
STAR_JOIN - the STAR_JOIN directive instructs the optimizer to favor a star join plan whenever possible.
STAR_JOIN—STAR_JOIN指令指示优化器尽可能地选择星型连接计划。
Sometimes we hope to influence the optimizer more directly, with minimum application changes if possible.
有时候，我们希望更直接地影响优化器，同时尽量避免更改应用程序。
Generally, the DB2 optimizer can smooth out performance deficiencies.
DB 2优化器通常可以解决性能方面的不足。
As shown in Figure 1, the DB2 optimizer chooses the best access path.
如图1所示，DB 2优化器选择最佳访问路径。
But first, you need to understand the path selected by the DB2 optimizer.
但是，首先需要了解DB 2优化器选择的路径。
However, if no indexes are available, the query optimizer must use a table scan.
但如果没有索引，则查询优化器必须扫描表。
However, if no indexes are available, the query optimizer must use a table scan.
但如果没有索引，则查询优化器必须扫描表。
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