I want to test query performance, so i clear cache in following way before each execution:
alter system flush buffer_cache;
alter system flush shared_pool;
But, first execution takes more time than second and consequent executions. For example first execution takes 30 seconds, consequent executions take 3 seconds.
Before each execution I clear the cache.
What can be the reason? I use TOAD for query execution. Does TOAD caches something after first execution?
And last question. Is there a dynamic query that query execution duration is stored?
Any help will be appreciated.