11G has a new feature called Invisible Indexes. An invisible index is invisible to the optimizer as default. Using this feature we can test a new index without effecting the execution plans of the existing sql statements or we can test the effect of dropping an index without dropping it.

CREATE DISKGROUP NORMAL REDUNDANCY
*For Oracle ASM to mirror files, specify the redundancy level as NORMAL REDUNDANCY (2- way mirroring by default for most file types) or HIGH REDUNDANCY (3-way mirroring for all files).

Explanation/Reference:
Explanation:
* The CREATE DATABASE ... ENABLE PLUGGABLE DATABASE SQL statement creates a new CDB. If you do not specify the ENABLE PLUGGABLE DATABASE clause, then the newly created database is a non-CDB and can never contain PDBs.
Along with the root (CDB$ROOT), Oracle Database automatically creates a seed PDB (PDB$SEED). The following graphic shows a newly created CDB:

* Creating a PDB
Rather than constructing the data dictionary tables that define an empty PDB from scratch, and then populating its Obj$ and Dependency$ tables, the empty PDB is created when the CDB is created. (Here, we use empty to mean containing no customer-created artifacts.) It is referred to as the seed PDB and has the name PDB$Seed. Every CDB non-negotiably contains a seed PDB; it is non-negotiably always open in read-only mode. This has no conceptual significance; rather, it is just an optimization device. The create PDB operation is implemented as a special case of the clone PDB operation.

Explanation/Reference:
Explanation:
The SQL Tuning Advisor takes one or more SQL statements as an input and invokes the Automatic Tuning Optimizer to perform SQL tuning on the statements. The output of the SQL Tuning Advisor is in the form of an advice or recommendations, along with a rationale for each recommendation and its expected benefit.
The recommendation relates to collection of statistics on objects (C), creation of new indexes, restructuring of the SQL statement (E), or creation of a SQL profile (A). You can choose to accept the recommendation to complete the tuning of the SQL statements.

A - OK
Start SQL*Plus and connect to the target database as the administrator who will transport the database with Data Pump import. This user must have DATAPUMP_IMP_FULL_DATABASE role to transport the database.
During the import operation, the database link must connect to a user on the source database with DATAPUMP_EXP_FULL_DATABASE role. The user on the source database cannot be a user with SYSDBA administrative privilege.
B - OK
Make all of the user-defined tablespaces in the database read-only.
D - OK
The source database and target database are running on the same platform with the same endianness.
http://docs.oracle.com/database/121/ADMIN/transport.htm#ADMIN13873