After a team member has entered actual data for an activity at measure level, a project administrator can accept the schedule in the next step. The data in the actual columns is then transferred to the plan and is thus fixed.
The transfer is very simple! All activities of a tree element (measure, package of measures or even project) can be transferred to the plan by right-clicking on the desired tree level and then selecting "Transfer activities to plan". The prerequisite for a transfer is that the corresponding plan field is empty. This prevents existing plans from being overwritten by mistake.
Activity: A task (or "To-Do" or "Milestone") that is assigned to a measure and is taken over by a person. Activities are managed at measure level.
Note: Should you ever want to transfer a schedule of a task from the actual columns to the plan and overwrite it with it. To do this, first delete the "old" plan values - also possible selectively - and then execute the above action.