The most likely place that ASO and OID would be used together is to deploy the enterprise user functionality. Enterprise users allow centralized management of database user accounts, enabling you to create, modify and delete users from many databases without ever logging on to those databases directly. You can also use the Enterprise User features to create userless schemas that allow creation of a database schema for owning objects even though there is no database user directly associated with that schema. Enterprise Users is generally considered where there are large numbers of accounts to manage with a large number of databases.
For more information about Enterprise Users, I'd recommend reviewing the Advanced Security Administrator's guide chapter on Enterprise Users. For the 9.2.0 documentation release, this is chapter 15 available at http://download-west.oracle.com/docs/cd/B10501_01/network.920/a96573/asomeus.htm.
This was first published in March 2004