===== Multitenant Architecture =====
==== Advantages ====
  * Database Consolidation
  * Reduced Costs
  * Rapid Implementation
  * Simplified Management
  * Separation of Duties
  * Simplified Tuning
  * Simplified Patching

==== Creating a CDB ====
Create spfile setting parameter ENABLE_PLUGGABLE_DATABASES = TRUE\\
Create instance by specifying STARTUP NOMOUNT\\
Create database using CREATE DATABASE command, adding new clause ENABLE_PLUGGABLE_DATABASES. \\
 If you are not using OMF you must either ... \\
 Use the SEED FILE_NAME_CONVERT option or set PDB_FILE_NAME_CONVERT in spfile \\
Connect to root and run scripts to create data dictionary\\

==== Opening / Closing Pluggable Databases ====
<code>SQL> alter session set container = pdb2;

Session altered.

SQL> shutdown 
Pluggable Database closed.
SQL> startup
Pluggable Database opened.
SQL> alter pluggable database pdb2 close;

Pluggable database altered.

SQL> alter pluggable database pdb2 open;

Pluggable database altered.</code>

I think it always safer to use the "alter pluggable" command so you definitely know which database you are closing.

Sometimes you may get an error when opening a pluggable database
<code>SQL> alter pluggable database pdb2 open;

Warning: PDB altered with errors.</code>

The "show pdbs" reveals that pluggable database pdb2 has been opened in restricted mode.
<code>SQL> show pdbs

    CON_ID CON_NAME			  OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
	 2 PDB$SEED			  READ ONLY  NO
	 3 PDB1 			  READ WRITE NO
	 4 PDB2 			  READ WRITE YES</code>

Use the view PDB_PLUG_IN_VIOLATIONS to see what the error is.\\
The full error message is not always written to the Alert Log.
<code>select time, message from pdb_plug_in_violations;

TIME                      MESSAGE
------------------------- --------------------------------------------------------------------------------
28-JUL-15 08.59.31.507182 Sync PDB failed with ORA-959 during 'CREATE USER c##ian IDENTIFIED BY *DEFAULT T
                          ABLESPACE "USERS" TEMPORARY TABLESPACE "TEMP" container = all'</code>
                          
In the above case I had forgotten to create the tablespace users in database pdb2.

==== Unplugging a PDB ====

<code>SQL> alter session set container=pdb2;

Session altered.

SQL> shutdown immediate;
Pluggable Database closed.
SQL> show pdbs

    CON_ID CON_NAME			  OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
	 4 PDB2 			  MOUNTED

SQL> conn / as sysdba
Connected.
SQL> alter pluggable database pdb2 unplug into '/home/oracle/pdb2.xml';

Pluggable database altered.

SQL> select pdb_name, status from dba_pdbs;

PDB_NAME	STATUS
--------------- ---------
PDB$SEED	NORMAL
PDB1		NORMAL
PDB2		UNPLUGGED

SQL> drop pluggable database pdb2;

Pluggable database dropped.</code>

==== Plugging In an Unplugged PDB ====
For this example I will simply plug back in the database that was dropped from above.\\
If I was moving the PDB to a new location on the server I would need to use the 'copy' parameter at the end of the command.
<code>SQL> create pluggable database pdb3 using '/home/oracle/pdb2.xml';

Pluggable database created.</code>

The database is in MOUNTED mode and must be opened after it has been created.\\
The Service Name was created automatically when the PDB was plugged in.