Oracle 12C引入了CDB与PDB的新特性，在ORACLE 12C数据库引入的多租用户环境（Multitenant Environment）中，允许一个数据库容器（CDB）承载多个可插拔数据库（PDB）。CDB全称为Container Database，中文翻译为数据库容器，PDB全称为Pluggable Database，即可插拔数据库。在ORACLE 12C之前，实例与数据库是一对一或多对一关系（RAC）：即一个实例只能与一个数据库相关联，数据库可以被多个实例所加载。而实例与数据库不可能是一对多的关系。当进入ORACLE 12C后，实例与数据库可以是一对多的关系。下面是官方文档关于CDB与PDB的关系图。
CDB组件（Components of a CDB）
一个CDB数据库容器包含了下面一些组件：
ROOT组件
ROOT又叫CDB$ROOT, 存储着ORACLE提供的元数据和Common User,元数据的一个例子是ORACLE提供的PL/SQL包的源代码，Common User 是指在每个容器中都存在的用户。
SEED组件
Seed又叫PDB$SEED,这个是你创建PDBS数据库的模板，你不能在Seed中添加或修改一个对象。一个CDB中有且只能有一个Seed.
PDBS
CDB中可以有一个或多个PDBS，PDBS向后兼容，可以像以前在数据库中那样操作PDBS，这里指大多数常规操作。
这些组件中的每一个都可以被称为一个容器。因此，ROOT(根)是一个容器，Seed(种子)是一个容器，每个PDB是一个容器。每个容器在CDB中都有一个独一无二的的ID和名称。
下面在12.2.0.1上做一些简单的CDB与PDB和维护管理示例
1、连接CDB数据库
还是使用sqlplus / as sysdba来连接，中之前的版本一样
[oracle@t13s admin]$ sqlplus / as sysdba
SQL*Plus: Release 12.2.0.1.0 Production on Wed Mar 15 10:39:52 2017
Copyright (c) 1982, 2016, Oracle. All rights reserved.
Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
SYS@testdb>2、查看数据库是否为CDB
SYS@testdb> select cdb from v$database;
CDB
---
YES如果为YES则为CDB如果为NO则为非CDB
3、查看当前的容器
SYS@testdb> show con_name
CON_NAME
------------------------------
CDB$ROOT此时连接的是root所以显示为CDB$ROOT，如果连接PDB则显示的是PDB的实例名
4、查看PDB的信息
--1
SYS@testdb> select con_id,dbid,guid,name,open_mode from v$pdbs;
CON_ID DBID GUID NAME OPEN_MODE
---------- ---------- -------------------------------- -------------------------------------------------- ----------
2 172801168 4AAD025C72A1F4B0E05358E8FF0AAC40 PDB$SEED READ ONLY
--2
SYS@testdb> show pdbs
CON_ID CON_NAME OPEN MODE RESTRICTED
---------- ------------------------------ ---------- ----------
2 PDB$SEED READ ONLY NO现在还没有创建PDB，所以只有一个PDB$SEED。
5、创建和删除PDB
使用CREATE PLUGGABLE DATABASE可以从SEED来创建一个PDB。当前的容器必须是CDB root。
SYS@testdb> show con_name
CON_NAME
------------------------------
CDB$ROOT
SYS@testdb> CREATE PLUGGABLE DATABASE test_pdb ADMIN USER testadm IDENTIFIED BY "rF" ROLES=(CONNECT) file_name_convert=('/data/oradata/testdb/pdbseed','/data/oradata/testdb/test_pdb') path_prefix='/data/oradata/testdb/test_pdb';
Pluggable database created.
SYS@testdb> show pdbs
CON_ID CON_NAME OPEN MODE RESTRICTED
---------- ------------------------------ ---------- ----------
2 PDB$SEED READ ONLY NO
3 TEST_PDB MOUNTED使用DROP PLUGGABLE DATABASE来删除PDB
drop pluggable database test_pdb including datafiles;6、启动和关闭PDB
--启动
SYS@testdb> alter pluggable database test_pdb open;
Pluggable database altered.
SYS@testdb> show pdbs
CON_ID CON_NAME OPEN MODE RESTRICTED
---------- ------------------------------ ---------- ----------
2 PDB$SEED READ ONLY NO
3 TEST_PDB READ WRITE NO
--关闭
SYS@testdb> alter pluggable database test_pdb close;
Pluggable database altered.
SYS@testdb> show pdbs
CON_ID CON_NAME OPEN MODE RESTRICTED
---------- ------------------------------ ---------- ----------
2 PDB$SEED READ ONLY NO
3 TEST_PDB MOUNTED7、容器间的切换
SYS@testdb> alter session set container=test_pdb;
Session altered.
SYS@testdb> show con_name
CON_NAME
------------------------------
TEST_PDB8、使用sql*plus直接连接PDB
查看监听，了解PDB是如何注册的
[oracle@t13s admin]$ lsnrctl status
LSNRCTL for Linux: Version 12.2.0.1.0 - Production on 15-MAR-2017 11:23:01
Copyright (c) 1991, 2016, Oracle. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=bossett13s)(PORT=1521)))
STATUS of the LISTENER
------------------------
Alias LISTENER
Version TNSLSNR for Linux: Version 12.2.0.1.0 - Production
Start Date 15-MAR-2017 09:35:52
Uptime 0 days 1 hr. 47 min. 10 sec
Trace Level off
Security ON: Local OS Authentication
SNMP OFF
Listener Parameter File /oracle/app/oracle/product/12.2/db/network/admin/listener.ora
Listener Log File /oracle/app/oracle/diag/tnslsnr/bossett13s/listener/alert/log.xml
Listening Endpoints Summary...
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=bossett13s)(PORT=1521)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1521)))
Services Summary...
Service "4abd62d724202b74e05358e8ff0a94fe" has 1 instance(s).
Instance "testdb", status READY, has 1 handler(s) for this service...
Service "test_pdb" has 1 instance(s).
Instance "testdb", status READY, has 1 handler(s) for this service...
Service "testdb" has 1 instance(s).
Instance "testdb", status READY, has 1 handler(s) for this service...
Service "testdbXDB" has 1 instance(s).
Instance "testdb", status READY, has 1 handler(s) for this service...
The command completed successfully需要配置tns
test_pdb =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = 10.255.232.88)(PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = test_pdb)
)
)连接
[oracle@t13s admin]$ sqlplus testadm/rF@test_pdb
SQL*Plus: Release 12.2.0.1.0 Production on Wed Mar 15 11:30:21 2017
Copyright (c) 1982, 2016, Oracle. All rights reserved.
Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
TESTADM@test_pdb>9、PDB中创建表空间
SYS@testdb> alter session set container=test_pdb
Session altered.
SYS@testdb> create tablespace users datafile '/data/oradata/testdb/test_pdb/users01.dbf' size 200m;
Tablespace created.
SYS@testdb> select name from v$tablespace;
NAME
------------------------------
SYSTEM
SYSAUX
UNDOTBS1
TEMP
USERS10、用户管理
在cdb中只能创建全局用户(c##开头),会在cdb和所有的pdb中创建该用户(但是pdb中的全局用户需要另外授权才能够在pdb中访问)。在pdb中只能创建的用户为本地用户
SYS@testdb> show con_name
CON_NAME
------------------------------
CDB$ROOT
SYS@testdb> create user test identified by "abcd";
create user test identified by "abcd"
*
ERROR at line 1:
ORA-65096: invalid common user or role name
SYS@testdb> create user c##test identified by "abcd";
User created.
SYS@testdb> alter session set container=test_pdb;
Session altered.
SYS@testdb> create user test identified by "abcd";
User created.参考：http://www.xifenfei.com/2013/05/oracle-12c-pdb-%E7%AE%A1%E7%90%86%E4%BB%8B%E7%BB%8D1.html
http://www.cnblogs.com/kerrycode/p/3386917.html
官方文档：http://docs.oracle.com/database/122/ADMIN/overview-of-managing-a-multitenant-environment.htm#ADMIN13507
