Sunday, February 9, 2014

what kinds of statistics oracle optimizer relying on


Table statistics

Number of rows
Number of blocks
Average row length

Column statistics

Number of distinct values (NDV) in a column
Number of nulls in a column
Data distribution (histogram)
Extended statistics

Index statistics

Number of leaf blocks
Number of levels
Index clustering factor

System statistics

I/O performance and utilization
CPU performance and utilization