From my knowledge i see savsys will run some time around 30min. In your case, i see that you want the system to be in down for an minimal amount of time.
In actual , savsys wil be perfomed under restricted state, it will get comprise of copy of lic, sec & cfg datas.
you can go for three separate saves,
savsys dev(tap01) omit(*secdta, *cfgdta) – Perfom this when the system to be restricted state(endsbs *all *immed)
savsecdta dev(tap01) – perform this when the system in active state
savcfgdta dev(tap01) – perform this when the system in active state
I guess by this, you can drastically reduce the savsys time, and reduce your downtime for the system.