You have attempted to retrieve a Repository object that does not exist. If multiple users are accessing the Repository concurrently, this error can occur if one user deletes a Repository object while a second user is attempting to retrieve the object. It can also occur if you are using an object identifier that has been saved from prior interactions with the Repository, and the object has been deleted between the time that you obtained the object identifier and the time that you attempted to retrieve the Repository object. Consider handling this exception with special processing for the case where a Repository object no longer exists.