All entries for Monday 06 March 2006

Cost Based Oracle

I began to read this book. I attended several presentations by this book’s author,Johnathan Lewis, in UKOUG conference and some were quite impressive.
This book is definitely a dream-killer. I cannot fall asleep after reading this, for you have to be very vigilant. I brought this book back to office.

P101: Columns order: put columns that appear with a range-based predicate toward the end of index definition; improve the compressibility of an index by putting the least selective(most repetitive) columns first

 
 cost  = blevel + 
            leaf_blocks * effective_index_selectivity +
           clustering_factor * effective_table_selectivity

effective_index_selectivity MIGHT = 1/distinct_keys (in user_indexes table)

P52 selectivity = “required range”divided by “total available range”

Hongfeng Sun : 06 Mar 2006 21:04 |  Tags: Oracle-Tune Review |  Comments (0) |  Close comments |  Report a problem