Why CBD_DATA_FILES and V$DATAFILE differs?

Though it is well documented in the Oracle 12c documentation, just to demo I wrote this post.

http://docs.oracle.com/cd/E16655_01/server.121/e17615/refrn009.htm#REFRN009

CDB_* Views

For every DBA_* view, a CDB_* view is defined. In the root of a multitenant container database (CDB), CDB_* views can be used to obtain information about tables, tablespaces, users, privileges, parameters, and so on contained in the root and in pluggable databases (PDBs).
CDB_* views are container data objects. When a user connected to the root queries a CDB_* view, the query results will depend on the CONTAINER_DATA attribute for users for the view. The CONTAINER_DATA clause of the SQL ALTER USER statement is used to set and modify users' CONTAINER_DATA attribute.
The CDB_* views are owned by SYS, regardless of who owns the underlying DBA_* view.
By default, a user connected to the root will only see data pertaining to the root.

In a PDB, the CDB_* views only show objects visible through a corresponding DBA_* view.
In addition to all the columns found in a given DBA_* view, the corresponding CDB_* view also contains the CON_ID column, which identifies a container whose data a given CDB_* row represents. In a non-CDB, the value of a CON_ID column will be 0.
Data returned by these views depends on whether a given PDB is open at the time the query is issued.

In particular, in an Oracle RAC environment, data returned by these view may vary according to the instance to which a session is connected.

List of action performed

1. Logged into CDB
2. Queried  both cbd_data_files and v$datafile , CDB_ view has only 7 rows
3. Queried V$PDBS to know status off PDBs
4. One PDB is in Mount state
5. Opened that PDB in read write mode.
6. Then we could see all the files.

SQL> set time on echo on
22:27:54 SQL> select name,cdb from v$database;

NAME      CDB                                                                  
--------- ---                                                                  
ORCL12C   YES                                                                  

22:28:14 SQL> sho con_name

CON_NAME                                                                       
------------------------------                                                 
CDB$ROOT                                                                       
22:28:20 SQL> set pages 20
22:28:54 SQL> select name from v$datafile;

NAME                                                                           
--------------------------------------------------------------------------------
D:\APP\TWELVEC\ORADATA\ORCL12C\SYSTEM01.DBF                                    
D:\APP\TWELVEC\ORADATA\ORCL12C\PDBSEED\SYSTEM01.DBF                            
D:\APP\TWELVEC\ORADATA\ORCL12C\SYSAUX01.DBF                                    
D:\APP\TWELVEC\ORADATA\ORCL12C\PDBSEED\SYSAUX01.DBF                            
D:\APP\TWELVEC\ORADATA\ORCL12C\UNDOTBS01.DBF                                   
D:\APP\TWELVEC\ORADATA\ORCL12C\USERS01.DBF                                     
D:\APP\TWELVEC\ORADATA\ORCL12C\PDBORCL\SYSTEM01.DBF                            
D:\APP\TWELVEC\ORADATA\ORCL12C\PDBORCL\SYSAUX01.DBF                            
D:\APP\TWELVEC\ORADATA\ORCL12C\PDBORCL\SAMPLE_SCHEMA_USERS01.DBF               
D:\APP\TWELVEC\ORADATA\ORCL12C\PDBORCL\EXAMPLE01.DBF                           

10 rows selected.

22:29:03 SQL> select file_name from cdb_data_files;

FILE_NAME                                                                      
--------------------------------------------------------------------------------
D:\APP\TWELVEC\ORADATA\ORCL12C\USERS01.DBF                                     
D:\APP\TWELVEC\ORADATA\ORCL12C\UNDOTBS01.DBF                                   
D:\APP\TWELVEC\ORADATA\ORCL12C\SYSAUX01.DBF                                    
D:\APP\TWELVEC\ORADATA\ORCL12C\SYSTEM01.DBF                                    
D:\APP\TWELVEC\ORADATA\ORCL12C\PDBSEED\SYSTEM01.DBF                            
D:\APP\TWELVEC\ORADATA\ORCL12C\PDBSEED\SYSAUX01.DBF                            

6 rows selected.

22:29:24 SQL> select con_id,name,open_mode from v$pdbs order by 1;

    CON_ID NAME                           OPEN_MODE                            
---------- ------------------------------ ----------                           
         2 PDB$SEED                       READ ONLY                            
         3 PDBORCL                        MOUNTED                              


22:31:08 SQL> alter pluggable database PDBORCL open read write;

Pluggable database altered.

22:31:25 SQL> select con_id,name,open_mode from v$pdbs order by 1;

    CON_ID NAME                           OPEN_MODE                            
---------- ------------------------------ ----------                           
         2 PDB$SEED                       READ ONLY                            
         3 PDBORCL                        READ WRITE                           

22:31:32 SQL> select file_name from cdb_data_files;

FILE_NAME                                                                      
--------------------------------------------------------------------------------
D:\APP\TWELVEC\ORADATA\ORCL12C\PDBSEED\SYSTEM01.DBF                            
D:\APP\TWELVEC\ORADATA\ORCL12C\PDBSEED\SYSAUX01.DBF                            
D:\APP\TWELVEC\ORADATA\ORCL12C\USERS01.DBF                                     
D:\APP\TWELVEC\ORADATA\ORCL12C\UNDOTBS01.DBF                                   
D:\APP\TWELVEC\ORADATA\ORCL12C\SYSAUX01.DBF                                    
D:\APP\TWELVEC\ORADATA\ORCL12C\SYSTEM01.DBF                                    
D:\APP\TWELVEC\ORADATA\ORCL12C\PDBORCL\SYSTEM01.DBF                            
D:\APP\TWELVEC\ORADATA\ORCL12C\PDBORCL\SYSAUX01.DBF                            
D:\APP\TWELVEC\ORADATA\ORCL12C\PDBORCL\SAMPLE_SCHEMA_USERS01.DBF               
D:\APP\TWELVEC\ORADATA\ORCL12C\PDBORCL\EXAMPLE01.DBF                           

10 rows selected.

22:31:45 SQL> spool off

Please provide your valuable suggestion/ corrections to improve
Thanks , Happy reading...