Below is an excerpt from Oracle document.

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I just want to confirm, is it correct to consider a user-created PDB or a seed PDB as a container? It's a little weird to me. If this is true. Then essentially everything is a container in an Oracle multi-tenant architecture. CDB root, system container, application container, PDBs, seed PDBs are all containers?

2 Answers 2


Yes, PDBs are containers.

Actually, the whole CDB is a container (CON_ID=0 called 'system container') which contains other containers:

  • CDB$ROOT is a container (CON_ID=1 'root') which is not a PDB

  • other containers which are PDBs:

  • PDB$SEED is a container (CON_ID=2) 'seed PDB'

  • other user-created PDBs (CON_ID>2)

Look at the diagram here: https://blog.dbi-services.com/oracle-12cr2-max_pdbs/


Well yes, a PDB is a container for the database objects of this PDB. However container in this context only means that it contains something (schema objects, not PDBs). This is most likely why the official names/descriptions in your listing are not named containers, even if they are. It is not (like the System or Application Container) a „housing“ for a PDB. (And to make things more confusing I would think of the Application Container more like a collection, not a container)

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