Multitenant database in Oracle 12c | Tech News

One of the new features of Oracle 12c is multitenant databases. Multiple databases can be plugged in a big container database.

Container database (CDB) is the primary database that comprises 0, 1 or many pluggable databases (PDB). This holds the controlfiles, datafiles, undo, tempfiles, redo logs and also the data dictionary for those objects that are owned by the root container. It is also called CDB$ROOT

Pluggable Database (PDB) – these are the databases stored within the primary container database. Each PDB is a set of schemas, objects and non-schema objects. PDB is made up of only datafiles and tempfiles to handle its own objects which includes its own data dictionary containing information about only those objects specific to the PDB. PDBs appear to the end users as a non-CDB database.

Seed PDB – A default PDB that the system uses as a template to provision other user-created PDBs. It is called PDB$SEED


Advantages of Multitenant database architecture

  • Multitenant architecture reduces the requirement to create multiple instances. It offers the ability to have 252 PDBS per multitenant CDB. This increases hardware utilization and so reduce capital expenses.
  • Upgrade and patching is made very simple. All underlying databases inside it are automatically upgraded and/or patched when the container database is upgraded/patched.
  • The plugged-in databases can easily plugged-out and moved to another container database. This way if one PDB is not ready to be upgraded/patched, it can be plugged-out instead of keeping the rest of the databases from being upgraded.
  • Fast deployment of a database to a new platform.
  • Fast provisioning of a new database.

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