This illustration shows a CDB with the following components:
The CDB has a CDB$ROOT
container.
A PDB$SEED
container is plugged into the root container.
Several PDBs are plugged into the root container.
Two application containers plugged into the root container.
Each application container has an application root container.
One application container has two application PDBs plugged into its application root container.
One application container has three application PDBs plugged into its application root container.
The application container with two application PDBs also has an application seed plugged into its application root container.