optimizer_index_caching question
- From: Ram K <lambu999@xxxxxxxxx>
- To: Oracle-L@xxxxxxxxxxxxx
- Date: Fri, 16 Dec 2005 07:15:41 -0500
Per 9i DB reference:
"OPTIMIZER_INDEX_CACHING<http://www.lc.leidenuniv.nl/awcourse/oracle/server.920/a96536/ch1137.htm#REFRN10142>lets
you adjust the behavior of cost-based optimization to favor nested
loops joins and IN-list iterators.... You can modify the optimizer's
assumptions about index caching for nested loops joins and IN-list iterators
by setting this parameter to a value between 0 and 100 to indicate the
percentage of the index blocks the optimizer should assume are in the
cache..... The default for this parameter is 0, which results in default
optimizer behavior"
Two questions on this:
1) In a working system, how do I find out the approximate percentage of
index blocks cached in SGA, so I can set the right value?
2) Wherever the value of optimizer_index_caching is not set, left to the
default of zero, does Oracle not use much indexes? I dont remember seeing
the value set in the OLTP systems that I worked with. (Maybe I didnt pay
enough attention?)
--
Thanks,
Ram.
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