PS - OA : Object Locking, Adaptive Callback

Even if the whole page is unused at the client it is returned only in pieces (object at a time) with respect to object call backs. If clients want to update many objects on the page, many callbacks result.
Hence PS - OA clients handle callback adaptively.

• If no transaction has a lock on any object in a page, then return the whole page (purge page from the cache).
• Otherwise return only the requested object. (As in PS - OO)

PS - OA Server tracks information of cached copies at the page level granularity. (PS - OO uses object granularity)