Based on the link blow , it is said , NSSn can run as multiple processes
How can I started more than one NSSn processes on my primary env ?
İf you have one more than log archive destination for remote. NSS proces has started for each remote log destination.
If redo transport services transmit redo data to multiple remote destinations, the LNSn processes (one for each destination) initiate the network I/O to all of the destinations in parallel.