A Persistable instance can be _prefetchable_. This means that the object can be loaded at startup by calling ODBA.cache.prefetch, and that it will never expire from the Cache. The prefetch status can be controlled per instance by setting the instance variable @odba_prefetch, and per class by overriding the module constant ODBA_PREFETCH
Once an object is no longer needed in memory a stub for that object is created and the object itself is garbage collected. A stub relates to the persistable for faster access to the object in the database. A stub is like a pointer to a persistable, a persistable that is no longer in memory. The persistable can be fetched back faster via the stub.
In odba the array and hash is redefined in the persistable class.