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Performance Tuning Intelligent Advisories

Oracle provides advisories for the buffer cache, MTTR (Mean Time To Recovery) and PGA target. It is important to note that setting the statistics_level parameter alone does not activate all of the advisories.  The Oracle9i Performance Tuning Guide and Reference provides information on activating and using advisories.

The Oracle Database Performance Tuning (1Z0-033) certification test will have a few questions on the new advisory feature in Oracle9i.  Test candidates should have a firm understanding of:

• The different advisories that are available in Oracle9i

  • Shared pool

  • Buffer pool

  • Undo segments
     

• How to activate the advisories including the use of the statistics_level parameter

Optimizer Dynamic Sampling

So little is known about the inner-workings of the cost based optimizer that is often called the Oracle database’s “little black box.”    The optimizer’s job is to analyze the statement being executed and determine the most efficient access path to the data for that statement. Craig Mullins provides an excellent description of a database optimizer in The DB2 Developer’s Guide  “the optimizer is equivalent to an expert system.  An expert system is a standard set of rules when combined with situational data can return an expert opinion.”
 

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