SAVSYS is part of the full system save.
Once a quarter we switch over to the backup system. Then we bring the
production system down into restricted state, do a full system save and
apply ptfs (which were loaded on to the system earlier set to apply at
next IPL). On Sunday evening we switch back to the production system. Not
only does this allow us to have a large save window but it allows us to
test switching back and forth. And actually running on the backup system
(granted, just on a weekend).
That's the only time tape touches the production system. All daily
backups are performed off of the backup system either via Mimix
replication or Domino replication.