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Adaptive Plans in Oracle Database 12c allow runtime changes to execution plans.
At runtime the cardinality of operations is checked and compared to the cardinality estimates used to generate the execution plan. If the cardinality of the operation is not as expected, an alternative subplan can be used.

To view the whole adaptive plan run the following after your SQL statement

SELECT * FROM TABLE(DBMS_XPLAN.display_cursor(format => 'adaptive'));

Use the following to also see the expected and actual cardinalities.

SELECT * FROM TABLE(DBMS_XPLAN.display_cursor(format => 'adaptive allstats last'));

With an adaptive plan you may see differences between the estimated rows (E-Rows) and actual rows (A-Rows).