Managing Oracle Multitenant Databases - OCP: Oracle Database 12c Administrator Certified Professional - page 552

In this chapter, we will explore how to manage the multitenant
database environment that is based on the Oracle Database 12 c
multitenant architecture. We will differentiate between multiten-
ant container databases (CDBs) and pluggable databases (PDBs).
The first topic of conversation is how to connect to CDBs and PDBs, and similarities to and
differences from establishing connections to non-CDBs. We will demonstrate establishing con-
nections through various exercises.
The second topic focuses on starting up and shutting down CDBs and then on opening
and closing PDBs. We will discuss the startup and shutdown options, as well as the open and
close options, and demonstrate use cases for each.
The third topic explores the impact of initialization parameter value changes on the CDB
and PDBs. We will list and discuss which parameters have an impact on the operation of the
multitenant environment.
Exam objectives are subject to change at any time without prior notice and
at Oracle's sole discretion. Please visit Oracle's Training and Certification
website ( http://www.oracle.com/education/certification/ ) for the
most current exam-objectives listing.
Establishing Connections to CDB/PDB
New to Oracle 12 c , the Oracle multitenant architecture is designed to allow an Oracle
database to host multiple Oracle databases within one overall structure. The multitenant
container database can includes zero, one, or many DBA-created pluggable databases.
From a client-connection perspective, a PDB looks like a traditional Oracle database and
is composed of schemas, schema objects, and non-schema objects. Oracle databases prior
to Oracle 12 c were non-CDBs.
Because the intent is for a PDB to appear as a non-CDB to the client connection, but in
reality the PDB exists in a host CDB, there are a few underlying differences that the DBA
must be aware of when establishing connections to the CDB and PDBs, starting up and
shutting down instances, and configuring initialization parameters.
In this section, we will discuss the ways to connect to a CDB and the various methods for
connecting to a PDB. We will discuss the types of accounts in a CDB, the common users, and
PDB users. Connecting to the CDB$ROOT should be an activity reserved for administrators and
system accounts. All users and custom applications should connect to PDBs. For a user con-
necting to a database, a PDB should appear to be just the same as a non-CDB.