Tuning: Memory Abusers

Question

Hello,
I'm working through the book Oracle Database 10g Performance Tuning Tips & Techniques from R. Niemiec. In chapter 15 is the topic - Top 10 "Memory Abusers" as a percent of all Statements - which I do not understand correct.
Maybe someone has this book and can help me on this?
I executed the sql-statement given in this book and it gives me about 66 percent for the top ten statements. The example has 44 percent.
I don't understand the ranking given for the example, for the example the result is 60 points. Why?
I don't know if I'm allowed to paste the rate-part here.
Greets,
Hannibal

Answer 1

I customized the query on 10g a little;
SELECT *
  FROM (SELECT rank() over(ORDER BY buffer_gets DESC) AS rank_bufgets,
               (100 * ratio_to_report(buffer_gets) over()) pct_bufgets,
               sql_text,
               executions,
               disk_reads,
               cpu_time,
               elapsed_time
          FROM v$sqlarea)
WHERE rank_bufgets < 11;In my opinion above query helps to find and prioritize the problematic queries which are run from the last database startup, so the magic number and the conditions are not so important :)
If you are on 10g and have the cost option AWR report of a problematic period or before 10g STATSPACK report will assist you for this purpose. Also after 10gR2 v$sqlstats is very useful, search and check them according to your version here; http://tahiti.oracle.com