P6 Scheduling problem

When i do F9(schedule), my activitis durations are moved (they are longer) for the number of days from the last scheduling.Why is that?I have no resourses assign to the activities... For example, start date 1.09.2006, duration 30 days(end date 30.09.2006), i do schedule at the date 10.09.2006, and duration is now 40 days!!

Is the remaining duration field updated as well? If you put in a start date on 01-09-2006, left the remaining duration at 30 days then scheduled the job with a data date of 10-09-2006 youll show a total duration of 40 days; 10 days since the activity started and 30 days remaining. You need to update how many days remain on the activity if your data data is before the activity completes. Hope that helps

Primavera does not assume progress like Microsoft Project does. If you have an activity planned that does not start, Primavera will reschedule the start of the activity at or after the data date. If you want to compare your current schedule progress to a target project, you have to establish a target and compare the current project to it. An afterthought & an extension of original question: In case you put the start date for the same example, and the activity hasnt started yet, but if you want it to stay there, and do schedule and the start date is now schedule data date, in that case you have to you have to constrain the date as a mandatory or expected start date.