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Oracle Performance Tuning stick
by unknown, a long time ago

Cost-Based Optimizer

  • autotrace: set autotrace on
  • trace logging(for tkprof): alter session set sql_trace=true
  • flush !buffer cache! (10g feature): alter session flush buffer_cache;

    This is the test harness I use to try out different ideas. It shows two vital sets of statistics for me:
  • The elapsed time difference between two approaches. It very simply shows me which approach is faster by the wall clock
  • How many resources each approach takes. This can be more meaningful then even the wall clock timings. For example, if one approach is faster then the other but it takes thousands of latches (locks), I might avoid it simply because it will not scale as well.

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