question on dbazine article
- From: "zhu chao" <chao_ping@xxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Thu, 26 Feb 2004 21:16:16 +0800
http://www.dbazine.com/burleson20.shtml
I often visit dbazine and read articlles there, on this issue, I have some
questions:
question to that article:
1. he said:
alter system set optimizer_index_cost_adj=20;
alter system set optimizer_index_caching=65.
but in fact, these parameters cannot be modified online. How did he do that?
2.Implement cursor_sharing=force
According to wait event based tuning, tuning something that is not the
bottleneck does not helps much. In his case, euqueue wait and full table scan
caused most of the problem. Would change cursor_sharing be the solution of his
problem?
3. question about add freelists;
He has 450 users inserting records, even if one person can insert a record
every 3 seconds, it is only possible that there is 150 new records per second.
Can't oracle process 150 record insert per second even if only 1 freelists? I
did a small test with 300 concurrent session doing insert into a table, each
insert a table after 3 second sleep. and this is the statspack report:( i
removed the plsql locker timer event from statspack via modifying
stats$idle_event).
Top 5 Wait Events
~~~~~~~~~~~~~~~~~ Wait % Total
Event Waits Time (cs) Wt Time
-------------------------------------------- ------------ ------------ -------
log file parallel write 25,955 2,345 90.72
control file parallel write 146 109 4.22
db file parallel write 168 55 2.13
buffer busy waits 30,761 34 1.32
--only a few percent of that.
log file switch completion 4 22 .85
Regards
Zhu chao.
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