## Part V Optimizer Statistics

The accuracy of an execution plan depends on the quality of the optimizer statistics.

This part contains the following chapters:

- Optimizer Statistics Concepts

Oracle Database**optimizer statistics**describe details about the database and its objects. - Histograms

A**histogram**is a special type of column statistic that provides more detailed information about the data distribution in a table column. A histogram sorts values into "buckets," as you might sort coins into buckets. - Configuring Options for Optimizer Statistics Gathering

This chapter explains what optimizer statistics collection is and how to set statistics preferences. - Gathering Optimizer Statistics

This chapter explains how to use the`DBMS_STATS.GATHER_*_STATS`

program units. - Managing Extended Statistics
`DBMS_STATS`

enables you to collect**extended statistics**, which are statistics that can improve cardinality estimates when multiple predicates exist on different columns of a table, or when predicates use expressions. - Controlling the Use of Optimizer Statistics

Using`DBMS_STATS`

, you can specify when and how the optimizer uses statistics. - Managing Historical Optimizer Statistics

This chapter how to retain, report on, and restore non-current statistics. - Importing and Exporting Optimizer Statistics

You can export and import optimizer statistics from the data dictionary to user-defined statistics tables. You can also copy statistics from one database to another database. - Analyzing Statistics Using Optimizer Statistics Advisor

Optimizer Statistics Advisor analyzes how optimizer statistics are gathered, and then makes recommendations.