CHAPTER 23Pluggable Databases

Oracle Multitenant (Pluggable Databases)

• New with Oracle Database 12c is Oracle Multitenant. This feature allows you to create and maintain many pluggable databases within an overarching multitenant container database.

• A multitenant container database (CDB) is defined as a database capable of housing one or more pluggable databases.

• A container is defined as a collection of data files and metadata that exist within a CDB. A pluggable database  is a special type of container that can be easily provisioned by cloning another database.

• If need be, a pluggable database can also be transferred from one CDB to another.

• Every CDB contains a master set of data files and metadata known as the root container.

• Each CDB also contains a seed container, which is used as a template for creating other pluggable databases. Each CDB consists of one master root container, one seed container, and zero, or one or more, pluggable databases.

Pluggable TermsContainer database (CDB), multitenant database A database capable of housing one or more pluggable databases

Pluggable database, (PDB) A set of data files and metadata that can be seamlessly transferred from one CDB to another

Root container A master set of data files and metadata containing information regarding all containers within a CDB. The root container is named CDB$ROOT.

Container A collection of data files and metadata. Can be root, seed, or a pluggable database.

Seed pluggable database A template of data files and metadata used to create new pluggable databases. The seed pluggable database is named PDB$SEED.

Plugging Associating the metadata and data files of a pluggable database with a CDB

Unplugging Disassociating the metadata and data files of a pluggable database from a CDB

Cloning Creating a pluggable database from a copy of another database (seed, PDB, or non-CDB)

CON_ID A unique identifier for each container within a CDB. The CDB-level views contain a CON_ID column that identifies the container with which the information being viewed is associated.

CDB data dictionary views Views that contain metadata regarding all pluggable databases within a CDB. These views only display meaningful information when queried via a privileged connection from the root container. The pluggable databases must be open for use.

non-CDB database An Oracle database created without the pluggable database feature enabled (the only type of database that was available prior to 12c)

Pluggable Architecture

Paradigm Shift• Allows DBA to manage many databases as one• B&R performed as if one database, but have the option of

backup and restore at pluggable level• Easily provision new databases• Pluggable can be created from seed, another pluggable,

or a non-CDB database

Containers: Strength in Numbers• Security• Granularity• Synergy• Provisioning• Transferability

Creating a CDB: initialization parameters

db_name='CDB'

enable_pluggable_database=true

audit_trail='db'

control_files='/u01/dbfile/CDB/control01.ctl','/u01/dbfile/CDB/control02.ctl'

db_block_size=8192

db_domain=''

memory_target=629145600

memory_max_target=629145600

open_cursors=300

processes=300

remote_login_passwordfile='EXCLUSIVE'

undo_tablespace='UNDOTBS1'

Create CDB Database StatementCREATE DATABASE CDB

MAXLOGFILES 16

MAXLOGMEMBERS 4

MAXDATAFILES 1024

MAXINSTANCES 1

MAXLOGHISTORY 680

CHARACTER SET US7ASCII

NATIONAL CHARACTER SET AL16UTF16

DATAFILE

'/u01/dbfile/CDB/system01.dbf' SIZE 500M

EXTENT MANAGEMENT LOCAL

UNDO TABLESPACE undotbs1 DATAFILE

'/u01/dbfile/CDB/undotbs01.dbf' SIZE 800M

SYSAUX DATAFILE

'/u01/dbfile/CDB/sysaux01.dbf' SIZE 500M

DEFAULT TEMPORARY TABLESPACE TEMP TEMPFILE

'/u01/dbfile/CDB/temp01.dbf' SIZE 500M

DEFAULT TABLESPACE USERS DATAFILE

'/u01/dbfile/CDB/users01.dbf' SIZE 50M

LOGFILE GROUP 1

('/u01/oraredo/CDB/redo01a.rdo') SIZE 50M,

GROUP 2

('/u01/oraredo/CDB/redo02a.rdo') SIZE 50M

USER sys IDENTIFIED BY foo

USER system IDENTIFIED BY foo

USER_DATA TABLESPACE userstbs DATAFILE

'/u01/dbfile/CDB/userstbsp01.dbf' SIZE 500M

ENABLE PLUGGABLE DATABASE

SEED FILE_NAME_CONVERT = ('/u01/dbfile/CDB','/u01/dbfile/CDB/pdbseed');

Creating a CDB with DBCA• Set OS variables

dbca -silent -createDatabase -templateName General_Purpose.dbc -gdbname CDB

-sid CDB -responseFile NO_VALUE -characterSet AL32UTF8 -memoryPercentage 30

-emConfiguration LOCAL -createAsContainerDatabase true

-sysPassword foo -systemPassword foo

Verifying CDB Details

SQL> select name, cdb from v$database;

SQL> select con_id, name from v$containers;

SQL> select con_id, file_name from cdb_data_files order by 1;

Tasks Administered from Root Container

• Starting/stopping instance• Enabling/disabling archive log mode• Managing instance settings that affect all databases within

the CDB, such as overall memory size• B&R of all data files within the database• Managing control files (adding, restoring, removing, and

so on)• Managing online redo logs• Managing the root UNDO tablespace• Managing the root TEMP tablespace• Creating common users and roles

Displaying Currently Connected Container

SELECT SYS_CONTEXT('USERENV', 'CON_ID') AS con_id,

SYS_CONTEXT('USERENV', 'CON_NAME') AS cur_container,

SYS_CONTEXT('USERENV', 'SESSION_USER') AS cur_user

FROM DUAL;

Common Users and Roles• Create while connected to SYS root container• Must use names starting with c##• Spans all containers

Creating a Pluggable Database• With the CREATE PLUGGABLE DATABASE statement,

you can use any of the following sources to create a pluggable database:• Seed database• Existing pluggable database (either local or remote)• Non-CDB database• Unplugged pluggable database

Managing a Listener in Pluggable Environment

• Oracle recommends that you create a service (besides the default service) for each pluggable databases

• Applications should connect to pluggable database via the manually created service

• Caution: If you have multiple CDB databases on one server, ensure that the pluggable database service names are unique across all CDB databases on the server. It’s not advisable to register two pluggable database databases with the exact same name with one common listener. This will lead to confusion as to which pluggable database you are actually connecting to.

Summary• New with Oracle Database 12c, a pluggable database is a collection of data

files and metadata that exist within a CDB. Pluggable databases have several interesting architectural features:

• When connected to a pluggable database, you have no visibility to other pluggable databases that exist within the CDB. It’s as if you are connected to an isolated database.

• Multiple pluggable databases share common database resources (memory structures, background processes, and so on) within the CDB. From the root container level, you can manage many DBA databases as if they were one database.

• You can shut down a pluggable database without affecting other pluggable databases within the CDB.

• New pluggable databases can be quickly created by cloning the seed database, an existing pluggable database, or a non-CDB.

• Pluggable databases can be easily transferred from one CDB to another by unplugging from one CDB and plugging the pluggable database into another CDB.