Oracle uses schemas (one per user) rather than separate databases. The important defaults are two schemas and two tablespaces that share similar names:
| Name | Kind | Description |
|---|---|---|
SYS |
Schema | Owns the data dictionary (USER$, OBJ$, the DBA_ views) |
SYSTEM |
Schema | Administrative account and tables |
SYSTEM |
Tablespace | Holds the data dictionary |
SYSAUX |
Tablespace | Auxiliary system data (AWR, Oracle Text, Spatial and others) |
Since 12.1.0.2, ALL_USERS.ORACLE_MAINTAINED marks every schema Oracle created, which any user can query:
SELECT username FROM all_users WHERE oracle_maintained = 'Y';See Database Names for enumerating schemas through SQL injection.