When the object is deleted, the programmers must know what objects have OIDs that contain the address of the deleted object. You refer to the objects that appear as rows of object tables by using their object identifiers. Applications are able to use references to navigate among the objects. Oracle8 allows a column of a table or element of a collection to contain OIDs. You can obtain a REF to a row object by selecting the object from its object table and applying the REF operator.
OID access is much faster than table joins.
You are able to establish relationships between tables without using foreign keys. Repeating Groups Application developers have used arrays for some time. An array is an ordered set of objects, called elements. The array uses an index of numbers to point to specific elements. All of the elements in an array must be of the same type.