[bbk2341] 第46集 - Chapter 09-Optimizing Sore Perations(01)

When to Gather Statistics

在10g、11g里面，搜集statistics信息分自动和手工方式两种.

Table Statistics

• Number of rows
• Number of blocks and empty blocks
• Average available free space
• Number of chained or migrated rows
• Average row length
• Last analyze date and smaple size
• Data dictionary view:dba_tables

查看表的统计信息，主要依据数据字典dba_tables

Index Statistics

• Index level(height)
• Number of leaf blocks and distinct keys
• Average number of leaf blocks per key
• Average number of data blocks per key
• Number of index entries
• Clustering factor:反应了表的排序程度.
• Data dictionary view:dba_indexes

Index Tuning Wizard

 

转载于:https://www.cnblogs.com/arcer/archive/2013/05/07/3064569.html