As you know With the release of Oracle Database 12c, Oracle introduced a major shift in database architecture: the Multitenant Architecture, also known as the CDB (Container Database) model. This marked a revolutionary step in how databases are managed. However, many organizations still rely on the traditional non-CDB structures. In this blog post, we’ll explore the technical differences between CDB and non-CDB and explain why the future clearly lies with the CDB model.
Let us start from beginning.
What is Non-CDB?
Non-CDB refers to the traditional standalone database architecture used in Oracle 11g and earlier versions. All components—data dictionary, system metadata, and user data—reside in a single unified structure.
What is CDB?
Introduced in Oracle 12c, the Multitenant Architecture allows one CDB to contain multiple PDBs (Pluggable Databases). This enables logical isolation of databases under one physical Oracle instance, simplifying management and improving scalability.
What is Difference:
Structural Comparison:
| Feature | CDB (Container Database) | Non-CDB (Traditional Database) |
|---|---|---|
| Architecture | Multi-tenant architecture | Single database instance |
| Portability | PDBs can be easily moved between CDBs | Requires export/import |
| Management | Centralized (manage all PDBs from one CDB) | Each database managed separately |
| Version Compatibility | Supported from 12c onwards (mandatory in 21c+) | Available up to 11g |
| Backup/Restore | Possible at the PDB level | Done for the whole database |
| Upgrade/Downgrade | Easier via PDB unplug/plug | Requires full database upgrade/downgrade |
CDB Structure:
CDB$ROOT: The root container that holds shared system metadata.PDB$SEED: The default template used to create new PDBs.PDB1,PDB2, …: User pluggable databases, each isolated and independent.- Each PDB contains its own
SYSTEM,SYSAUX,USERS, andTEMPtablespaces.
Non-CDB:
- A single-layer structure where all system and user objects reside in the same unified space.
Operational Advantages
- Patching Simplicity: Apply patches at the CDB level to affect all PDBs, saving time and effort.
- Database Portability: Easily unplug a PDB and plug it into another CDB.
- Resource Consolidation: Host multiple databases under one Oracle instance, reducing overhead.
Do not forger!!! Starting with Oracle 21c, the non-CDB architecture is no longer supported. All new databases must be created using the multitenant model. Furthermore, new features in Oracle 23c (like AI Vector Search, JSON Relational Duality) are only available within CDBs.
Happy CDB’s 🙂
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