If
the stream protocol for this stream instance specifies that the stream is
a split stream, then this field indicates which stream instance has allocated
buffers that this stream will use. In this case, the Sync/Stream Manager
does not allocate a new set of stream buffers for this stream. If this
stream instance is not a split stream, the Sync/Stream Manager ignores this
field, but it will be passed to the source and target stream handlers.