Forecast frozen zone calculation

This topic describes how LN checks whether changes to the forecast occur inside the frozen zone- or the frozen zone+, compared to the previously sent revision.

For a general overview of the frozen-zones functionality, refer to Forecast frozen zones.

Calculation details

The details of the calculation of the frozen zones are as follows:

LN retrieves the frozen zones from the Frozen Zone + field and the Frozen Zone - field in the Planning Terms and Conditions (tctrm1135m000) session.
To select the relevant version of the terms and conditions agreement, LN takes the start date of the first period after the current date as the effective date.
On the customer side, to obtain the end of the frozen zone plus, LN adds the number of days from the Frozen Zone + field to the current date. In the same way, LN calculates the frozen zone minus by using the value of the Frozen Zone - field. On the supplier side, LN performs a similar calculation, but LN uses the receipt date of the forecast instead of the current date.
LN does not calculate this date against any specific calendar; all calendar days are counted.
LN checks the forecast against the forecast in the previously sent revision. If no earlier revision is present, LN presumes the previous forecast zero (0).
LN adds the forecast before the current date to the first period after the current date.
Similarly, for the previously sent revision, LN adds the forecast before the date that revision was sent to the first period after the date sent.
If the current forecast and preceding revision of the forecast have the same number of periods, and the start dates of these periods are the same, LN performs the frozen-zone check separately for each period. Otherwise, LN uses the sum of the forecasts of all periods within the horizon and only checks the totals.
If the forecast increases in the frozen zone+, compared to the previous revision, or if these values decrease in the frozen zone-, the system concludes that the frozen-zone restrictions have been violated.

These checks are always initiated from the sessions where you approve or accept a forecast. LN can respond in various ways to a failed frozen-zone check. For more information, refer to To use the frozen zone restrictions.

Example

In the following example, the frozen zone+ and the frozen zone- are 20 days.

Period	Period Start Date	Forecast Revision 1	Current Forecast
1	April 2	15	15
2	April 9	20	20
3	April 16	20	25
4	April 23	20	15
5	April 30	20	20
6	May 7	25	25
7	May 14	25	50
8	May 21	25	20

Characteristic dates
Forecast revision 1 sent	April 10	Period 2
Current date	April 13	Period 2
Horizon	May 3	Period 5

The current date falls in period 2 and the horizon falls in period 5; therefore, LN checks periods 3, 4, and 5.

LN adds the forecast of periods 1 and 2 to period 3, because the date sent of revision 1 and the current date are in period 2.

For forecast revision 1, the forecast for period 3 becomes 55 (15+20+20). For the current forecast, the forecast for period 3 becomes 60. That increase is not permitted in the frozen zone plus.

Suppose the customer adjusts the current forecast of period 3 from 60 to 55, and tries again. Now, period 3 passes the test, but period 4 shows a decrease from 20 to 15, and the frozen-zone-minus check fails.

Period 5 is accepted.

Period 6 is not checked, because that period is beyond the frozen-zone horizon.

Example

In following example, the frozen zone+ and the frozen zone- are 20 days.

Period	Period Start Date	Forecast Revision 1	Current Forecast
1	April 2	15
2	April 9	20
3	April 16	20	5
4	April 23	20	15
5	April 30	20	20
6	May 7	25	25
7	May 14	25	60
8	May 21	25	30

Characteristic dates
Forecast revision 1 sent	April 10	Period 2
Current date	April 19	Period 3
Horizon	May 9	Period 6

The current date falls in period 3; therefore, LN checks periods 4, 5, and 6.

For forecast revision 1, LN adds the forecast of periods 1 and 2 to period 3, because the date sent of revision 1 is in period 2. However, period 3 does not need to be checked.

For the current forecast, LN adds the forecast of period 3 to period 4, because the current date is in period 3.

For the current forecast, the forecast for period 4 becomes 20 (5+15). This value equals the forecast of period 4 in forecast revision 1. Therefore, period 3 does not need to be checked.

Period 5 and 6 are also accepted.