A tablespace is a logical storage container for segments. Segments are database objects, such as tables and indexes, that consume storage space.

In a multitenant container database (CDB), each pluggable database (PDB) and application root has its own set of permanent tablespaces, which correspond to physical data files:

• One SYSTEM tablespace, which includes the data dictionary; tables and views that contain administrative information about the database; and compiled stored objects such as triggers, procedures, and packages.
• One SYSAUX tablespace, which is an auxiliary tablespace to the SYSTEM tablespace. It is the default tablespace for many Oracle Database features and products that previously required their own tablespaces, so it reduces the number of tablespaces required by the database.
• One or more undo tablespaces. In local undo mode (which is the default), the database automatically creates an undo tablespace in every PDB. In shared undo mode, a single-instance CDB has only one active undo tablespace exists, and an Oracle Real Application Clusters (Oracle RAC) CDB nas one active undo tablespace for every instance. All undo tablespaces in shared undo mode are visible in the data dictionaries and related views of all containers.

• Zero or more user-created tablespaces , which contain the data for user-defined schemas and objects in the PDB. You can store user data in the default USERS tablespace or create additional tablespaces for specific application data or system data.

Each container also has a temporary tablespace , which correspond to physical temp files. One default temporary tablespace exists for the CDB root and for each application root, application PDB, and PDB. Temporary tablespaces contain transient data that persists only for the duration of a session. No permanent schema objects can reside in a temporary tablespace.

• Permanent Tablespaces
• SYSAUX Tablespace
• SYSTEM Tablespace
• Tablespaces in a Multitenant Environment
• Temporary Tablespaces
• Undo Tablespaces