Extents are logical representations of all persistent instances of a given persistence-capable class, possibly including subclasses.

Extents are obtained through the PersistenceManager's getExtent method. This method takes two parameters: the class of objects the Extent contains, and a boolean indicating whether or not subclasses are included as well.

You can only retrieve Extents for persistence-capable classes whose metadata specifies a value of true for the requires-extent attribute (this is the default).