36 Overview of Managing a Multitenant Environment

Components of a CDB

A CDB includes the following components:

• Root

  The root, named CDB$ROOT, stores Oracle-supplied metadata and common users. An example of metadata is the source code for Oracle-supplied PL/SQL packages. A common user is a database user known in every container. A CDB has exactly one root.

• Seed

  The seed, named PDB$SEED, is a template that you can use to create new PDBs. You cannot add objects to or modify objects in the seed. A CDB has exactly one seed.

• PDBs

  A PDB appears to users and applications as if it were a non-CDB. For example, a PDB can contain the data and code required to support a specific application. A PDB is fully backward compatible with Oracle Database releases before Oracle Database 12c.

Each of these components is called a container. Therefore, the root is a container, the seed is a container, and each PDB is a container. Each container has a unique container ID and name within a CDB. Figure 36-1 shows a CDB with several PDBs.

Figure 36-1 CDB with PDBs

Description of "Figure 36-1 CDB with PDBs"

You can easily plug a PDB into a CDB and unplug a PDB from a CDB. When you plug in a PDB, you associate the PDB with a CDB. When you unplug a PDB, you disassociate the PDB from a CDB. An unplugged PDB consists of an XML file that describes the PDB and the PDB's files (such as the data files and wallet file).

You can unplug a PDB from one CDB and plug it into a different CDB without altering your schemas or applications. A PDB can be plugged into only one CDB at a time.

Each PDB has a globally unique identifier (GUID). The PDB GUID is primarily used to generate names for directories that store the PDB's files, including both Oracle Managed Files directories and non-Oracle Managed Files directories.

Common Users and Local Users

A CDB supports common users. A common user is a user that has the same identity in the root and in every existing and future PDB. A common user can log in to the root and any PDB in which it has privileges. The operations that a common user can perform depend on the privileges granted to the common user. Some administrative tasks, such as creating a PDB or unplugging a PDB, must be performed by a common user. A CDB also supports local users. A local user is a user that exists in exactly one PDB.

Separation of Duties in CDB and PDB Administration

Some database administrators manage the entire CDB. These database administrators connect to the CDB as common users, and they manage attributes of the entire CDB and the root, as well as some attributes of PDBs. For example, these database administrators can create, unplug, plug in, and drop PDBs. They can also specify the temporary tablespace for the entire CDB and the default tablespace for the root, and they can change the open mode of one or more PDBs.

Database administrators can also connect to a specific PDB as a local user and then perform a subset of management tasks on the PDB that a database administrator performs on a non-CDB. The subset of tasks are those required for the PDB to support an application. For example, these can include management of tablespaces and schemas in a PDB, specification of storage parameters for that PDB, and changing the open mode of the current PDB.

Tasks for a Multitenant Environment

A multitenant environment enables you to achieve the goals described in "Purpose of a Multitenant Environment". To do so, you must complete the following general tasks:

• Task 1, "Plan for the Multitenant Environment"

• Task 2, "Create One or More CDBs"

• Task 3, "Create, Plug In, and Unplug PDBs"

• Task 4, "Administer and Monitor the CDB"

• Task 5, "Administer and Monitor PDBs"

Task 1   Plan for the Multitenant Environment

Creating and configuring any database requires careful planning. A CDB requires special considerations. For example, consider the following factors when you plan for a CDB:

• The number of PDBs that will be plugged into each CDB

• The resources required to support the planned CDB

• Configuration options that apply to the entire CDB and configuration options that apply to each PDB

See "Planning for CDB Creation" for detailed information about planning for a CDB.

Task 2   Create One or More CDBs

When you have completed the necessary planning, you can create one or more CDBs using either the Database Configuration Assistant (DBCA) or the CREATE DATABASE SQL statement. In either case, you must specify the configuration details for each CDB.

See "Using DBCA to Create a CDB" and "Using the CREATE DATABASE Statement to Create a CDB" for detailed information about creating a CDB.

After a CDB is created, it consists of the root and the seed, as shown in Figure 36-2. The root contains minimal user data or no user data, and the seed contains no user data.

Figure 36-2 A Newly Created CDB

Description of "Figure 36-2 A Newly Created CDB"

Task 3   Create, Plug In, and Unplug PDBs

PDBs contain user data. After creating a CDB, you can create PDBs, plug unplugged PDBs into it, and unplug PDBs from it whenever necessary. You can unplug a PDB from a CDB and plug this PDB into a different CDB. You might move a PDB from one CDB to another if, for example, you want to move the workload for the PDB from one server to another.

See Chapter 38, "Creating and Removing PDBs with SQL*Plus" and Chapter 39, "Creating and Removing PDBs with Cloud Control" for information about creating PDBs, plugging in PDBs, and unplugging PDBs.

Figure 36-3 shows a CDB with several PDBs.

Figure 36-3 A CDB with PDBs

Description of "Figure 36-3 A CDB with PDBs"

Task 4   Administer and Monitor the CDB

Administering and monitoring a CDB involves managing the entire CDB, the root, and some attributes of PDBs. Some management tasks are the same for CDBs and non-CDBs, and some are different. See "After Creating a CDB" for descriptions of tasks that are similar and tasks that are different. Also, see Chapter 40, "Administering a CDB with SQL*Plus", Chapter 41, "Administering CDBs and PDBs with Cloud Control", and Chapter 43, "Viewing Information About CDBs and PDBs with SQL*Plus".

You can use Oracle Resource Manager to allocate resources among PDBs in a CDB and within individual PDBs. See Chapter 44, "Using Oracle Resource Manager for PDBs with SQL*Plus".

You can also use Oracle Scheduler to schedule jobs in a CDB and in individual PDBs. See Chapter 46, "Using Oracle Scheduler with a CDB".

Task 5   Administer and Monitor PDBs

Administering and monitoring a PDB is similar to administering and monitoring a non-CDB, but there are some differences. See Chapter 41, "Administering CDBs and PDBs with Cloud Control", Chapter 42, "Administering PDBs with SQL*Plus", and Chapter 43, "Viewing Information About CDBs and PDBs with SQL*Plus".

Tools for a Multitenant Environment

Use the following tools to complete tasks for a multitenant environment:

• SQL*Plus

  SQL*Plus is a command-line tool that enables you to create, manage, and monitor CDBs and PDBs. You use SQL statements and Oracle-supplied PL/SQL packages to complete these tasks in SQL*Plus.

  See SQL*Plus User's Guide and Reference.

• DBCA

  Oracle Database Configuration Assistant (DBCA) is a utility with a graphical user interface that enables you to configure a CDB, create PDBs, plug in PDBs, and unplug PDBs.

  See Oracle Database 2 Day DBA, Oracle Database Installation Guide, and the DBCA online help for more information about DBCA.

• Oracle Enterprise Manager Cloud Control

  Cloud Control is a system management tool with a graphical user interface that enables you to manage and monitor a CDB and its PDBs.

  See the Cloud Control online help for more information about Cloud Control.

• Oracle SQL Developer

  Oracle SQL Developer is a graphical version of SQL*Plus that gives database developers a convenient way to perform basic tasks.

  See Oracle SQL Developer User's Guide.

• The Server Control (SRVCTL) utility

  The SRVCTL utility can create and manage services for PDBs.

  See "Managing Services Associated with PDBs".

• EM Express

  Note:

  PDB management with EM Express is available starting with Oracle Database 12c Release 1 (12.1.0.2).

  EM Express supports managing PDBs, including creating PDBs from the seed, cloning PDBs, plugging in PDBs, unplugging PDBs, and dropping PDBs. EM Express also supports basic resource management like setting CPU utilization and storage limits at the PDB level and changing the resource plan at CDB level.

  See Oracle Database 2 Day DBA for more information.

• Oracle Multitenant Self-Service Provisioning application

  Note:

  This feature is available starting with Oracle Database 12c Release 1 (12.1.0.2).

  This application enables the self-service provisioning of PDBs. CDB administrators control access to this self-service application and manage quotas on PDBs.

  For more information about the application or to download the software, use any browser to access the OTN page for the application:

  http://www.oracle.com/goto/multitenant

  To access the application, click the Downloads tab, and select Multitenant Self-Service Provisioning in the Oracle Database 12c Multitenant Applications section.