Keyword: shows the difference.
*Full ADDM analysis across two AWR snapshot periods Detects causes, measure effects, then correlates them Causes: workload changes, configuration changes Effects: regressed SQL, reach resource limits (CPU, I/O, memory, interconnect) Makes actionable recommendations along with quantified impact
*Identify what changed / Configuration changes, workload changes
*Performance degradation of the database occurs when your database was performing optimally in the past, such as 6 months ago, but has gradually degraded to a point where it becomes noticeable to the users. The Automatic Workload Repository (AWR) Compare Periods report enables you to compare database performance between two periods of time.
While an AWR report shows AWR data between two snapshots (or two points in time), the AWR Compare Periods report shows the difference (ABE) between two periods (or two AWR reports with a total of four snapshots). Using the AWR Compare Periods report helps you to identify detailed performance attributes and configuration settings that differ between two time periods.
Reference: Resolving Performance Degradation Over Time

With adaptive SQL plan management, DBAs no longer have to manually run the verification or evolve process for non-accepted plans. When automatic SQL tuning is in COMPREHENSIVE mode, it runs a verification or evolve process for all SQL statements that have non-accepted plans during the nightly maintenance window. If the non-accepted plan performs better than the existing accepted plan (or plans) in the SQL plan baseline, then the plan is automatically accepted and becomes usable by the optimizer. After the verification is complete, a persistent report is generated detailing how the non-accepted plan performs compared to the accepted plan performance. Because the evolve process is now an AUTOTASK, DBAs can also schedule their own evolve job at end time.
Note:
* The optimizer is able to adapt plans on the fly by predetermining multiple subplans for portions of the plan.
* Adaptive plans, introduced in Oracle Database 12c, enable the optimizer to defer the final plan decision for a statement until execution time. The optimizer instruments its chosen plan (the default plan) with statistics collectors so that it can detect at runtime, if its cardinality estimates differ greatly from the actual number of rows seen by the operations in the plan. If there is a significant difference, then the plan or a portion of it will be automatically adapted to avoid suboptimal performance on the first execution of a SQL statement.

Explanation
http://docs.oracle.com/database/121/ADMIN/dbrm.htm#ADMIN11852

RMAN> ALTER TABLESPACE sysaux OFFLINE IMMEDIATE;
RMAN> RESTORE TABLESPACE sysaux;
RMAN> RECOVER TABLESPACE sysaux;
RMAN> ALTER TABLESPACE sysaux ONLINE;
* Example:
While evaluating the 12c beta3 I was not able to do the recover while testing "all pdb files lost".
Cannot close the pdb as the system datafile was missing...
So only option to recover was:
Shutdown cdb (10)
startup mount; (1)
restore pluggable database
recover pluggable database
alter database open;
alter pluggable database name open;
Oracle support says: You should be able to close the pdb and restore/recover the system tablespace of PDB.
* Inconsistent backups are usually created by taking online database backups. You can also make an inconsistent backup by backing up data files while a database is closed, either:
/ Immediately after the crash of an Oracle instance (or, in an Oracle RAC configuration, all instances)
/ After shutting down the database using SHUTDOWN ABORT
Inconsistent backups are only useful if the database is in ARCHIVELOG mode and all archived redo logs created since the backup are available.
*Open the database with theRESETLOGSoption after finishing recovery:
SQL> ALTER DATABASE OPEN RESETLOGS;

Explanation/Reference:
Explanation:
Note:
* DBMS_REDACT.FULL completely redacts the column data.
* DBMS_REDACT.NONE applies no redaction on the column data. Use this function for development testing purposes. LOB columns are not supported.
* The DBMS_REDACT package provides an interface to Oracle Data Redaction, which enables you to mask (redact) data that is returned from queries issued by low-privileged users or an application.
* If you create a view chain (that is, a view based on another view), then the Data Redaction policy also applies throughout this view chain. The policies remain in effect all of the way up through this view chain, but if another policy is created for one of these views, then for the columns affected in the subsequent views, this new policy takes precedence.