If a DLL handler is not loaded, it will be loaded and connected to the Sync/Stream Manager at this point. All device driver stream handlers are loaded during CONFIG.SYS processing at operating-system startup.
Each stream handler can be a source or target or both for any stream instance. Therefore, a target HID for a stream is required if it can be a target, and a source HID is required if it can be a source. If the stream handler is NULL, the source HID and target HID are the same. If a stream handler can be used only as a target stream handler, the source HID returned is 0. If a stream handler can be used only as a source stream handler, the target HID returned is 0.