You normally create a planning delivery schedule from internal planning data even before you have received information on requirements from the customer. When you later receive a forecast delivery schedule from the customer, you create a new planning delivery schedule by overwriting schedule lines in the previous planning delivery schedule with actual requirements.

Schedule lines from the forecast delivery schedule that lie within the split validity period are split and copied. For future periods, however, you may decide to include schedule lines from the previous planning delivery schedule to complement information from the forecast delivery schedule. When you set the "Adopt schedule lines" indicator, the system adopts unchanged into the new planning delivery schedule those schedule lines in the previous planning delivery schedule whose dates lie completely after the validity period end date.