Statistics Analysis【TUNNING 12】【每日一译】--2013-1-20

The query optimizer relies on object statistics to generate execution plans. If these
statistics are stale or missing, the optimizer does not have the necessary information it
needs and can generate poor execution plans. The Automatic Tuning Optimizer checks

each query object for missing or stale statistics, and produces two types of output:

查询优化器依赖于对象的统计信息去创建执行计划。如果这些统计信息是旧的或者丢失，

那么优化器将没有它需要的信息和不能产生很好的执行计划。ATO核对每个查询的对象

的旧的信息和丢失的信息，并且产生2种类型的输出：

■ Recommendations to gather relevant statistics for objects with stale or no statistics.
Because optimizer statistics are automatically collected and refreshed, this
problem may be encountered only when automatic optimizer statistics collection

has been turned off. See "Automatic Statistics Gathering" on page 14-2.

#推荐去收集对象的相关统计信息对于使用旧的和丢失统计信息的对象。因为优化器的

统计信息是自动收集和刷新的，但它会遇到一个问题当自动优化统计信息的收集被关闭时候。

■ Auxiliary information in the form of statistics for objects with no statistics, and
statistic adjustment factor for objects with stale statistics.

This auxiliary information is stored in an object called a SQL Profile.

#辅助信息对于对象的统计信息的形式是没有包含统计信息，并且对于对象来说统计信息的调整

使用旧的统计信息。

这个辅助信息存在于一个叫做SQL PROFILE的对象里。