36 Overview of Managing a Multitenant Environment

A CDB includes the root, the seed, and PDBs.

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.

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 container in which it has been granted CREATE SESSION privilege. 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.

Some database administrators manage an entire CDB, while others manage individual PDBs.

The database administrators who manage an entire CDB 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 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 PDB administrator 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, changing the open mode of the current PDB, and setting PDB-level initialization parameters.

A multitenant environment enables you to achieve several goals. Complete general tasks to configure and use a multitenant environment.

These goals are 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

• Container management policies executed as an aggregate on the entire CDB or executed locally on individual PDBs

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 only Oracle maintained objects and data structures, and the seed is a generic seed database for cloning purposes.

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 Creating and Removing PDBs with SQL*Plus and 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 Administering a CDB with SQL*Plus, Administering CDBs and PDBs with Cloud Control, and Viewing Information About CDBs and PDBs with SQL*Plus.

You can use Oracle Resource Manager to allocate and manage resources among PDBs hosted in a CDB, and you can use it to allocate and manage resource use among user processes within a PDB. See 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 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 Administering CDBs and PDBs with Cloud Control, Administering PDBs with SQL*Plus, and Viewing Information About CDBs and PDBs with SQL*Plus.

You can use various tools to configure and administer 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.