In Oracle Database 12c, adaptive query optimization is a set of capabilities that enables the optimizer to make run-time adjustments to execution plans and discover additional information that can lead to better statistics. Adaptive optimization is helpful when existing statistics are not sufficient to generate an optimal plan.
Below are a series of blog posts that I have written, that explains the Basics of how these features work.
Below are some oracle white papers and Mos notes that you could read, to familiarize yourselves with these new features.
Parameter Recommendations for Oracle 12c – Part 1 (Upgrade PM Blog)
Parameter Recommendations for Oracle 12c – Part 2 (Upgrade PM Blog)
Things to consider before upgrading to 126.96.36.199 (Upgrade PM Blog)
Adaptive Query Optimization configuration : Parameters, Preferences and Fix controls (Christian Antognini Blog)