You use this function to structure the tasks that belong to a project in a hierarchy.
You can only use summary tasks in bottom-up scheduling.
In Customizing for Collaboration Projects you specified that task hierarchies are allowed, by choosing Structure → Define Project Types.
Task hierarchies are formed when you create subtasks for tasks.
You cannot create subtasks for tasks directly below the project definition.
You specify in Customizing whether you want to use task hierarchies with or without summary tasks.
Once you create a subtask for a task, this task becomes a summary task. Some activities can only be carried out for tasks that are not summary tasks. These include:
· Confirming time
· Entering qualifications
· Assigning project roles
· Planning work
· Assigning cost and revenue rates
Some of the information from the subtasks is aggregated in the summary task.
You can perform all activities at any level of the task hierarchy. There are no summary tasks.