Is schedule per-user only?
 

I'm getting ready to do a system update and I don't want SD to run until I'm sure everything is OK. The usual user of this system has a SD schedule; the user I log in as for upgrade stuff has none. Is it safe to assume that no SD backups will happen until the usual user logs in? I could log in as that user and turn off the scheduled backups but it's a bit of a chore (a number of backups of and to different volumes).

Correct: schedules do not run if the user is not logged in.