If managerial work is characterized by variety, fragmentation, and brevity, how do managers perform basic management functions such as planning, which would seem to require reflection and analysis?
Essentially, you are asking how managers are able to do things like planning, which take thought, at the same time that they are having to deal with the immediate demands of every day business operations. The answer to this is that they must work hard and long and create their long-range plans at times when they do not have issues that must be dealt with immediately.
Ideally, a manager will create long term plans and will then use those plans to inform his or her actions on a daily basis. The manager must find the time to make those plans. This is not always easy, but it is necessary. Once the plans are made, they will provide the manager with something of a "road map." They will help the manager have a good idea of where they are trying to go. Knowing this will help the manager deal in a systematic and logical way with the variety of issues that come up in day to day operations and need to be solved immediately.
Managers can find time in their busy and fragmented schedules for planning and reflection by carrying out other tasks more efficiently. For example, they can delegate tasks to trusted subordinates, eliminate lengthy or wasteful meetings that can be supplanted by e-mails or other communications, make communications such as letters and e-mails more succinct, and prioritize what needs to get done within a certain time frame. By saving time in their schedule, they can actually schedule time for functions such as planning and reflection. That is, they can create time in which their task is to think about the future and reflect on the past. In addition, they can carve out time to go on retreats and to have planning meetings with other colleagues so that they can dedicate time to in-depth reflection. If managers do not make planning and reflection a priority and save time for it in their schedules, then it will likely not always happen.