When an object is dereferenced, the liveCache data area that contains the before-images of persistent objects must satisfy the consistent view of the instance.
Before-images are sorted according to their age, from old to new.
Normally, only those before-images that are no longer accessed by a consistent view are deleted.
In exceptional cases, memory problems can result in the deletion of before-images that can still be accessed.
In these cases, liveCache can no longer retrieve the requested view of the instance.
The older the consistent view, the greater the likelihood of this phenomenon.