In Oracle 12c, in a plug-gable database environment, we
can create a single database container, and plug multiple databases into this
container. All these databases then share the exact same oracle server/background
processes and memory, unlike the previous versions where each database has its
own background processes and shared memory. This helps in database
consolidation and reduces the overhead of managing multiple desperate
databases.
Container Database (CDB): Are the
core data dictionary objects that come after an Oracle database installation.
Pluggable
Database (PDB):
Data dictionary objects and data related to the application. We can have many PDB
plugged into a single CDB.
A new admin role "CDB
Administrator" has been introduced in Oracle 12.1 release databases.
Multiple databases can then share a
master LGWR process, but have their own dedicated LGWR process within the
container.
All Oracle database options/features
are available on the PDB level.
RMAN backup
at CDB level.
We can
unplug a PDB from a CDB to another CDB.
PDB's can be cloned inside the CDB.
Management of PDB (clone/creation/plug/unplug/drop) are implemented as SQLs.
Extremely fast PDB-provisioning (clone inside the CDB), because each CDB comes
with a “PDB Seed”.
Database patch/upgrade management very quick as CDB is a
single point of installation.
Each PDB has its own data dictionary.
Data Guard configuration on CDB as whole
RMAN point-in-time recovery at PDB level
(while other PDB's remains open)
Resource Manager is extended for creating, unplugging, plugging
in, and cloning, dropping or even setting up for the open mode of the PDB.
Flashback of
a PDB should be available for Oracle12c Release 2.
Entire containers can be backed up in single run, regardless
of how many databases they contain.
Upgrade
one container database and all pluggable databases are upgraded.
New
Commands
create pluggable database
alter pluggable database
drop pluggable database