sundar

Can any one advice  why clarity advices to set Optimizer Mode = Choose for

Discussion created by sundar on Sep 27, 2009
Hi,  In Clarity 8.1 / v12 Installation Guide the Oracle Optimizer Mode adviced to set for Clarity is Choose.Pls find below.     The required mode for CA Clarity PPM is CHOOSE. This is the Oracle-recommended mode and is the default value.
Optimizer mode CHOOSE relies on statistics about tables and indexes being available. It uses those statistics to determine the
best path of execution for a query. Those statistics need to be refreshed under certain circumstances such as when the schema changed
or the data volume changed. The process of refreshing those statistics is called analyzing the schema .      It is good for 9i ,but is it advisable for oracle 10G too.    For oracle 10G i found many DB gurus advised (in the net) to set optimizer_features_enable = 10.2.0.2 and optimizer_mode = FIRST_ROWS_n or ALL_ROWS for a warehouse)  but remove the 9i CHOOSE default.    Another View-->  Optimizer_mode=choose -- 10g now ignores this and uses the default of ALL_ROWS.See Oracle metalink note 189702.1 for more information.
 Using the RULE mode may result in unpredictable behaviour of the optimizer.  Can any one advice me (CA guys) why  it is  advised in clarity to set Optimizer Mode = Choose for 10g too...  Cheers,Sundar

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