The Oracle Database Buffer Cache should it be bigger…

During the years I heard lots of stories about sizing the Oracle Database Buffer Cache. Oracle introduced in Oracle 8i (8.1.7) the view V$DB _CACHE_ADVICE. According the documentation this view shows IO’s that would be performed at various cache sizes from 10% to 200% of the current size. For example (GV$DB_CACHE_ADVISE):

The thing what is crossing my mind all the time is the question, will a system really react the way the advisor is predicting? This question is a very obvious question of course and in this post I like to place a nice little discussion in place.
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