Release 1 of Oracle 12c also introduced the Adaptive Plans and Adaptive Statistics functionality, known collectively as Optimizer Adaptive Features, intended to enhance system and query performance based on dynamic system activity. These options are enabled by default, and are controlled by the combined parameter OPTIMIZER_ADAPTIVE_FEATURES. In cases of OnBase performance degradation with Oracle 12c Release 1, Hyland Software has noted improved performance when the Adaptive Features have been disabled.
Oracle has changed the way these features work and how they can be selectively enabled with 12c Release 2. This revised behavior has also been made available in 12c Release 1 through post-release patches.
Follow the recommendations outlined by Oracle in Oracle Support Note #2312911.1 for Oracle 12c Release 1. The default Optimizer Adaptive Features parameter values can be used with Oracle 12c Release 2.