Diagnosis
In Customizing, you determined that no new schedule lines can becreated in the planning time fence, nor can existing schedule lines bechanged. If a change occurs within the planning time fence, the systemdisplays an error message.

System Response
New schedule lines are not created within the planning time fence.

Procedure
Check the dates of your schedule lines or check the planning time fencein Customizing (Demand management -> Indep.requirements -> Fixing).