About Multitenant Container Databases

Multitenant architecture, introduced in Oracle Database 12c Release 1 (12.1), enables an Oracle database to function as a multitenant container database (CDB) that includes zero, one, or many customer-created pluggable databases (PDBs). A PDB is a portable collection of schemas, schema objects, and nonschema objects that appears to any Oracle client application as a non-CDB. Note: all Oracle database versions prior to Oracle Database 12c Release 1 (12.1) are known as non-CDBs.

A CDB contains one seed database, which is a system-supplied template that the CDB can use to create new PDBs. The seed PDB is named PDB$SEED. You cannot add or modify objects in PDB$SEED. Because new PDBs are essentially copied from the seed rather than created from scratch, PDB creation time is generally much faster than creating a non-CDB.

PDBs can also be cloned from other PDBs in a similarly fast amount of time.

PDBs can be unplugged, which means they are removed from the CDB, and exist on the database server simply as a set of files: a metadata XML file along with some database files (.DBFs). This combination of metadata file and database files can then be easily plugged into any other CDB that is compatible with the PDB. For compatibility requirements, see PDB and CDB Compatibility.

From the point of view of .NET developers who have SYSDBA privileges, this makes testing a database configuration with your application as simple as cloning an existing PDB, or plugging in a PDB in the form of some provided database files. Similarly, a database configuration can be shared with other developers, either by cloning or through unplugging and sharing the database files.

If a user with SYSDBA privileges makes a connection to a CDB in Visual Studio Server Explorer, a Pluggable Databases Node appears in the tree control. When that node is expanded, the seed PDB, along with any other available PDBs, appear as child nodes. From there, operations such as Create New, Plug, Unplug, Clone, Delete, Open, and Close can all be easily achieved.

For more information on the multitenant architecture and its benefits, see Oracle Database Concepts and the Oracle Database Administrator's Guide.