SYSAUX

Prior to Oracle9i Database, if the DEFAULT TABLESPACE was not specified when the user was created, it would default to the SYSTEM tablespace. If the user did not specify a tablespace explicitly while creating a segment, it was created in SYSTEM—provided the user had quota there, either explicitly granted or through the system privilege UNLIMITED TABLESPACE. To solve this problem we may create default tablespace in oracle 9i.

ALTER DATABASE DEFAULT TABLESPACE ;

We can verify default tablespace for a database using following command:

SELECT PROPERTY_VALUE FROM DATABASE_PROPERTIES
WHERE PROPERTY_NAME = 'DEFAULT_PERMANENT_TABLESPACE';

Several schemas such as the intelligent agent user DBSNMP, data mining user ODM are not directly related to user operations, but are important to database integrity nonetheless. Some of these schemas used to have SYSTEM as their default tablespace.
Oracle Database 10g introduces a new tablespace called SYSAUX that holds the objects of these schemas. This tablespace is created automatically during database creation and is locally managed. The only change allowed is the name of the datafile.This approach supports recovery when the corruption of SYSTEM requires a full database recovery. Objects in SYSAUX can be recovered as any normal user object while the database itself remains operational.