Object Oriented Databases The Hierarchical Solution

The Hierarchical Solution: Early hierarchical databases would maintain references between objects (or data structures) by storing the actual physical location of the referenced object. This was convenient because you could stream a large amount of data from memory to disk and simply replace the memory pointers with the physical pointers.

This solves the problem of volatility in the address, but exposes a new one: The physical location of the referenced object may have to change if the object changes. If the physical location changes, the references that use that physical location have to change as well.

In a hierarchical database, this means that when an object’s physical location changes, some process must find all the references and modify them. The penalty for physically moving an object makes working with a hierarchical database extremely awkward for both the database designers and for the end users, except for very constrained applications.