The SYSTEM and SYSAUX tablespaces are mandatory tablespaces.
They are created at the time of database creation.
They must be online.
The SYSTEM tablespace is used for core functionality (for example, data dictionary tables).
The auxiliary SYSAUX tablespace is used for additional database components (such as the Enterprise Manager Repository).
Each Oracle database contains a SYSTEM tablespace and a SYSAUX tablespace. They are automatically created when the database is created. The system default is to create a smallfile tablespace. You can also create bigfile tablespaces, which enable the Oracle database to manage ultralarge files (up to 8 exabytes).
A tablespace can be online (accessible) or offline (not accessible). The SYSTEM tablespace is always online when the database is open. It stores tables that support the core functionality of the database, such as the data dictionary tables.
The SYSAUX tablespace is an auxiliary tablespace to the SYSTEM tablespace. The SYSAUX tablespace stores many database components, and it must be online for the correct functioning of all database components.
