A very important part of the process of incremental delivery is the weekly commitment. Each week the product owner and the development team should agree on an increment of value. The development team will commit to delivering that value, and the whole organisation should respect that commitment.
So if anyone wants the team to do something different – a few hours’ support, or an urgent feature for a desperate customer – they must expect the team to say ‘no’. Because the team has promised the product owner that it will spend its time delivering the agreed value.
The time to choose what the team does is at the weekly planning. Or preferably before the weekly planning, in conversation with the product owner. If you anticipate support interrupts, get them allocated into that week’s increment. And if you failed to anticipate them, find a way to let the team deliver on its commitment anyway. After all, on average you’ll only have a couple of days to wait.
The way to influence how the team spends its time is to influence the product owner. To directly ask the team to do something that isn’t in the increment is to fail to respect their commitment to the product owner. No-one performs well when asked to steer in two different directions at the same time, and no-one should be asked to decide where their loyalties lie. Agile software methods all place the product owner at the gateway between the team and any parties who may wish to use their time. Entering the team’s room via the back door breaks the fundamental structure of the agile process, and will likely lead to confusion, disaffection, loss of morale and loss of productivity. And all for the sake of a couple of days…