Oracle 12c feature:

1.Oracle 12c, introduced the concept of "online statistics gathering".

2.By default there are seven predefined maintenance windows,weekend maintenance windows are longer in duration than the weekday maintenance windows.

SELECT WINDOW_NAME,REPEAT_INTERVAL,DURATION,to_char(LAST_START_DATE,'dd.mm.yyyy hh24:mi') "laststart",to_char(NEXT_START_DATE,'dd.mm.yyyy hh24:mi') "nextstart",ENABLED "window enabled?",ACTIVE "window open?"
FROM DBA_SCHEDULER_WINDOWS WHERE RESOURCE_PLAN='DEFAULT_MAINTENANCE_PLAN';

3.Invisible column.
Defined as invisible, the column won’t appear in generic queries, unless the column is explicitly referred to in the SQL statement or condition, or DESCRIBED in the table definition.
SQL> CREATE TABLE emp (eno number(6), ename name varchar2(40), sal number(9) INVISIBLE);
SQL> ALTER TABLE emp MODIFY (sal visible);

4.Multiple indexes on the same column.
only one type of index is usable/visible at a given time. In order to test the invisible indexes, you need to set the optimizer_use_use_invisible_indexes=true.
SQL> CREATE INDEX emp_ind1 ON EMP(ENO,ENAME);
SQL> CREATE BITMAP INDEX emp_ind2 ON EMP(ENO,ENAME) INVISIBLE;

5.How to execute SQL statement in RMAN
In 12c, you can now execute any SQL and PL/SQL commands in RMAN without the need of a SQL prefix:
RMAN> SELECT username,machine FROM v$session;
RMAN> ALTER TABLESPACE users ADD DATAFILE SIZE 121m;

6.Table level recovery in RMAN