Oracle multitenant database architecture gives the ability to virtualize oracle database implementations, similarly to OS virtualization.   The multitenant architecture has two main components:  The CDB – Container Database and PDB – Pluggable database.  These two components have many aspects which help to describe their architecture and are detailed below:

CDB – Container Database

1. CDB is commonly referred to as the root container.
2. One root container in any implementation and contains all oracle provided metadata and common user.
3. CDB$ROOT is the name of the root container.
4. All PDBs belong to a single root container.
5. User or application data should never stored in the root.
6. You can have common users for system administration in root that crosses all PDB in the root container.
7. One seed PDB exist in all root containers, Oracle supplies this template to create new PDB.

PDB – Pluggable Database

1. PDB$SEED is the name of the seed PDB in all root container databases.
2. You cannot add or modify objects in PDB$SEED.
3. Zero or more user-created PDBs in CDB.
4. PDBs are entities that contain application data and code for specific features.
5. PDBs do not contain oracle supplied metadata or common users.
6. No PDBs exist at CDB creation.
7. PDBs are uniquely named in a CDB.
8. PDBs name must be unique across multiple CDB if using the same listener.

Larry Catt

OCP