Yes, you may disconnect completely while being active. How you adjust to not having the pump on will vary according to your exercise, your BG pre-exercise, food intake and other factors like if you have been running low/high/"normal", phase of the moon, sunspots, etc.
I try to lower my basal about an hour before exercise, then I keep a close watch via the CGM for trending to see if I need to adjust that basal rate. For me, bolusing my basal in advance would send me into a pretty substantial hypo. I do frequently find that I need to raise my basal rate for 2-3 hours after the exercise has ended, and then I lower my basal overnight to stave off an exercise-induced low from 2 - 4 a.m.
The ability to make those fine-tuned temporary basal rates is one of the things that has me sold on the pump. BTW, none of this fine-tuning means that I spend all my time between 70-140, it just means I spend less time below 70 or over 140 (not to mention less time with low/high symptoms).