| # Purchase schedules and Enterprise Planning In ERP LN, the purchase of JIT items is handled through purchase schedules. This topic describes how Enterprise Planning handles the purchase planning of these items. During an order simulation in Enterprise Planning, purchase volumes are usually planned as planned purchase orders. However, ERP LN can also transfer purchase orders to a purchase schedule in the Purchase Control module of Order Management. ERP LN does so, if: The order simulation is run for the actual scenario. You selected the Purchase Schedule in Use check box in the Item - General (tcibd0101s000) session for the item involved. If you run the Generate Order Planning (cprrp1210m000) session, ERP LN determines whether a shortage exists for a particular item for the simulated time period, and takes into account the demand, the firm supply, and for what exact moments possible shortages exist. If a shortage occurs, ERP LN generates supply. If ERP LN uses a purchase schedule to plan supply for an item, ERP LN does not generate planned purchase orders, but stores a purchase volume in an internal memory. When ERP LN generated all the required purchase volumes for the item, ERP LN groups the ordered purchase volumes in between two delivery moments in one purchase-schedule line, and lot sizes the purchase volumes according to the lot-size rules. General constraints During an order-based planning run, ERP LN checks if shortages exist for the purchase schedule items. If so, ERP LN records the supply of these items in schedule lines that it set on the delivery moments that you generated in the Generate Planned Delivery Moments (tdipu0225m000) session for the supplier involved in the purchase schedule. If the purchase schedule is shipment-based ERP LN lists these planned delivery moments in the Planned Delivery Moments (Shipment Based) (tdipu0125m000) session; if the purchase schedule is delivery based, ERP LN lists the planned delivery moments in the Planned Delivery Moments (Delivery Based) (tdipu0126m000) session. In the order-based planning process, ERP LN carries out a rescheduling step to match supply with demand. The way in which this rescheduling mechanism works for purchase scheduled items differs slightly from the way ERP LN applies this mechanism for items that are not planned through purchase schedules. The following constraints apply for purchase schedule items: ERP LN always disables the Only Reschedule Total Order Quantity check box in the EP Parameters (cprpd0100m000) session for purchase schedule items. Purchase schedule lines always behave as if the Planned Order before Firm/Actual check box in the EP Parameters (cprpd0100m000) session where selected. ERP LN can only reschedule schedule line quantities to delivery moments. Horizons and Frozen Zones ERP LN uses a specific horizon and a frozen zone to plan purchase schedule items. The horizon end date of a purchase schedule is the date until which ERP LN displays delivery moments in the Planned Delivery Moments (Shipment Based) (tdipu0125m000) session or the Planned Delivery Moments (Delivery Based) (tdipu0126m000) session. ERP LN groups all the requirements between two delivery moments into one purchase schedule. ERP LN groups purchase volumes that fall between the last defined delivery moment and the horizon end date to a schedule line for the last delivery moment. Beyond the horizon end date, where no predefined delivery moments exist, ERP LN inserts required purchase volumes into the purchase schedule, but does not lotsize, nor group the purchase volumes to a delivery moment. After the contract related to the purchase schedule expires, ERP LN translates the required purchase volumes to planned purchase orders for an empty supplier and generates a signal to inform the planner. Beyond the horizon end date, where no predefined delivery moments exist, ERP LN translates required purchase volumes into planned purchase orders for an empty supplier and generates a signal to warn the planner. For plan items, ERP LN uses a time fence as a period during which ERP LN cannot modify the supply plan and the planned orders. However, for the firm part of purchase schedule items, ERP LN uses a: Frozen Period: the time period during which Enterprise Planning cannot generate or update purchase schedule lines. Frozen Zone - : the time period calculated from the current date and during which ERP LN takes into account a lowerbound, which means that the schedule line quantities can increase, but not decrease. Enterprise Planning can create new schedule lines for new demand, but cannot delete existing schedule lines in this period. Frozen Zone + : the time period calculated from the current date and during which ERP LN takes into account an upperbound, which means that the schedule line quantities can decrease, but not increase. Enterprise Planning cannot generate new schedule lines in this period, but the quantities of the existing lines can be lowered. Purchase schedule items and time fences In addition to the frozen zone-, the frozen zone+, and the frozen period, you can set a time fence in the Items - Planning (cprpd1100m000) session for items for which the Purchase Schedule in Use check box in the Items - General (tcibd0501m000) session is selected. Although the use of a time fence for purchase schedule items leads to complex and unclear results, the reason for this functionality is that you can have multiple sources for a plan item. You can have several clusters for an item - each with a different cluster. Possibly, only one of these items has a purchase schedule, while the other items are distributed or manufactured items. Therefore, you can enter a time fence for plan items with a purchase schedule. However, if you do enter a time fence, ERP LN displays a warning. Note You cannot use purchase schedules for project items, or for distribution items (items with the cluster segment filled). Note You cannot set capacity constraints in Enterprise Planning for purchase schedule items, because purchase schedules already contain capacity. Therefore, the capacity constraints fields in the Items - Purchase Business Partner (tdipu0110m000) session are disabled for purchase schedule items. Note You can use a sourcing strategy and/or a supply strategy for purchase schedule items. If you use a supplying strategy, supply can entirely or partly be planned based on purchase schedules. Example frozen zone and horizon
X | delivery moment
S | schedule line
R | Requirement
In Figure 1-1, the time span of the purchase schedule is divided in four periods. The figures show how both Order Management, and Enterprise Planning model the existing situation, and how ERP LN handles requirements that occur in Enterprise Planning: Period 1 is the frozen period. ERP LN cannot touch the volumes recorded in the schedule lines in this period. Enterprise Planning cannot plan supply in this period. To avoid supply from being originated by requirements that result from an order-planning or master-planning run end up in this period, Enterprise Planning generates a rescheduling message which advises you to plan the supply to another delivery moment on a date outside period 1. In period 2, the frozen zone+, ERP LN cannot add new schedule lines, but only decrease the quantities of the schedule lines in this period. To avoid that requirements resulting from an order-planning or a master-planning run end up in this part of the purchase schedule, Enterprise Planning can generate rescheduling messages. In period 3, the purchase schedule can be regenerated, and subsequently the schedule lines (delivery moments) are not yet defined. Enterprise Planning groups all the requirements that it generated during a planning run to the delivery moments, and then sends these requirements to the Purchase (PUR) module of Order Management where the requirements are used to update the corresponding schedule line. In period 4, Figure 1-1 shows that no more delivery moment are available. As a result, Enterprise Planning considers every date as a potential delivery moment, and does not group the requirements anymore, but sends them directy to the PUR module of Order Management. Example planning and rescheduling Figure 1-2 shows the existing demand for a purchase schedule item. All the time moments are in the frozen zone-, and t1 falls after the frozen zone+. In addition the following is true:
Min. Lot Size | 8
Demand on t2 | 5 pcs
Demand on t3 | 10 pcs
Demand on t5 | 5 pcs
Pattern moment 1 | on t1
Pattern moment 2 | on t4
1-2 Planning and rescheduling purchase schedule items
X | planned delivery moment
FZ+ | frozen zone +
FZ- | frozen zone -
ERP LN must fill the demand placed on t2 and t3 in time, which is why ERP LN generates supply of 15 pieces on t1, that is, the closest planned delivery moment available. ERP LN must fill the second demand of 5 pieces, placed on t5, with a supply of 8 pcs (minimum lot size) on planned delivery moment t4 (see Figure 1-3). 1-3 Planning supply for a purchase schedule item
S1 | schedule line 1
S2 | schedule line 2
Figure 1-4 shows how ERP LN reacts if the demand placed on t3 increases with 5 pieces. 1-4 Rescheduling supply for a purchase schedule item ERP LN carries out the folowing steps during an order-based planning run, if the demand placed on t3 increases by five pieces (see Figure 1-3): The schedule lines S1 and S2 are recognized as firm planned because these lines are in the frozen zone-. However, the lines are firm planned in the sense that ERP LN can still increase the ordered quantity, not decrease it. Generate a rescheduling message Reschedule into %1$u001 %2$U001.. In other words, ERP LN advices you to reschedule five pieces of schedule line 2 into schedule line 1. ERP LN adds 2 pieces to schedule line 2 to be able to fill the demand placed on t5. Figure 1-5 shows the way in which ERP LN reacts if the demand placed on t3 increases by ten pieces. 1-5 Rescheduling supply for a purchase schedule item ERP LN carries out the folowing steps during an order-based planning run, if the demand placed on t3 increases with 10 pieces (see Figure 1-5): The schedule line are recognized as firm planned in the sense that ERP LN can still increase the ordered quantity, but not decrease it. Generate a rescheduling message Reschedule into %1$u001 %2$U001.. In other words, ERP LN advices you to reschedule eight pieces of schedule line 2 into schedule line 1. ERP LN adds 5 pieces to schedule line 2 to be able to fill the demand placed on t5. Note If Enterprise Planning cannot update the purchase schedule, it generates a planned purchase order for the same supplier. Note that Enterprise Planning blocks planned purchase orders for purchase schedule items at the moment of transferring planned orders to the execution level. Related topics Plan items in Enterprise Planning Sales schedules in Enterprise Planning |