Property :: registerHandle - Register property handle
In order to receive server events caused by other applications in a client server environment one may register a property handle to be notified in such cases. Notifications are sent only, when the resource affected by an update or delete operation is currently used by this property handle, i.e. when the currently selected instance changes or the index for the currently selected access key has changed.
Notifications are not sent on attribute level, but on instance and collection level. The property handle is registered for being notified when an event happens on the allocated resources (index or instance). Notification events have to be handled in appropriate event handlers implemented in the property or type context class ( DBBaseContext :: notifyRemove (), ...).
The function has no effect when being called in a local, replication or file server application. The function registers only ones. Further calls for registering the handle will be ignored.
When the property handle is not valid, the function throws an exception.
Handling server events causes asynchronous processing, since server events are send as soon as the server detects the event. Since property handles are not thread save, notification handler should lock property handles or simply set a switch in the application, which is handled later.