Introduction

In this blog I will provide insights to a  Detailed Scheduling process  and  the configuration of control  constraints, rules, and parameters  to  consider different types of relationship between planning objects (Orders, operations, activities) during detailed scheduling and optimization.

Since Pegging and  order internal  relationships  in PP/DS are commonly known and well-documented functions I will focus in this article on external / cross-order relationship   and provide a template how you can setup  your own  custom service heuristic to maintain external cross-order relationships.

This own  service heuristic can be used as template for an own developed heuristic in a project or as heuristic to prototype the planning with cross-order / external relationship.

Target audience of the blog are experts (Solution Architects, Consultants or PP/DS Developer) in  Manufacturing for Planning & Scheduling (PP/DS)  who are interested or  responsible for the implementation of production planning and scheduling with SAP  S/4HANA.

S/4HANA Manufacturing for Planning & Scheduling

As an important and integral part of the material planning process, S/4HANA Manufacturing for Planning & Scheduling …

• provides feasible and optimal production schedules
• multi-level planning in one shot
• considering all constraints ( material flow, capacity and others…)
• optimization, automated planning (Optimizer, Service-Heuristic…)
• possibility flexibly extend and/or adjust planning logic (customization, BADIs, Custom Developed Heuristic …)

Planning and Scheduling in PP/DS can consider different types of relationship between planning objects in scheduling.

By the Optimizer or Strategy profile you can define whether the system must consider during detailed scheduling  the product availability (pegging relationships)  and/or whether the system must retain time relationships between operations/activities into account. (order internal or cross-order as external relationship)

Focus of this blog will be an SAP Template function as service heuristic that maintains order external relationship.

Pegging

Pegging is used to assign suitable existing product receipts and product stocks, which can cover the requirement, to a product requirement. Pegging organizes the material flow through all BOM levels, from the procurement of components and raw materials to the delivery of a sales order, for example.

Orders that are linked together, and their pegging relationships, form a Pegging structure.

The picture below gives an example of a pegging structure. The arrows represent the pegging relationships; that is the material flow.

Example End-to-End Pegging Relationship

Pegging be used by subsequent procedures.

Based on pegging relationships, the system can:

• Identify planning problems on various production levels and display them using alerts.
• Automatically forward scheduling specifications for an order to the dependent orders in the pegging structure, in Detailed Scheduling
• Optimize delays and storage costs in PP/DS optimization.

For details refer to SAP help: Pegging

There are two different types of pegging relationships: fixed and dynamic.

Fixed pegging enables you to fix a pegging relationship. The fix pegging relationship will not be changed automatically by the system. See also SAP Note “458996 – Fixed pegging in SAP APO (documentation)”

For pegging relationships to be created, the product, location, account assignment (make-to-stock and make-to-order production) and planning version must be the same.

For details “Considering Pegging Relationships” in Detailed Scheduling refer to SAP help : Considering Pegging Relationships

Pegging should not be confused with the net requirements calculation: During planning, using the net requirements calculation, the system identifies shortages in order to then create receipts to remove these shortages. If the MRP has taken place, a pegging network will be established based on it.

Considering Time Relationships

Two activities of can be linked by a time relationship that specifies a minimum or maximum interval between the activity dates.

Taking relationships between activities into consideration means scheduling or rescheduling activities so that no minimum or maximum intervals are violated.

The following types of relationship exist:

Order-internal relationships

These include operation-internal relationships between activities in the same operation and cross-operation relationships between activities from different operations of the same order.

Cross-order relationships

external relationships link activities of different orders like  internal relationships.

For details refer to SAP help: Considering Time Relationships

Considering order-internal relationships

The PP/DS  system considers cross-operation time relationships when there are maintained relationships between activities with minimum and maximum intervals and  in the strategy profile it is specified  whether system is to consider time relationships and intervals.

The minimum and maximum intervals between operations are defined  by  queue times of an operation, and  the wait times and transportation times.

There is a certain complexity to calculating relationship durations and implementing them in production orders and source of supply in PP/DS (PDS) and is not always easy to understand at first glance.

For details refer to SAP note “604878 – R/3->APO Relship duration w/ interoperation times, overlaps”

The  note 604878 describes in detail the calculation of the durations of the relationships of two directly consecutive operations and also provides tips for dealing with situations where the visible durations in the PP/DS manufacturing order or in the PP/DS source of supply ( PDS) or the operation dates in the PP/DS manufacturing order appear to make no sense.

This note will discuss only operations for which interoperation times were defined in the form of wait times, transportation times or queue times.

The following  times are analyzed as interoperation times from ERP  to PP/DS:

• The process-related and minimum wait time
• The minimum and standard queue time
• The minimum and standard transportation time

With these times the minimum and maximum constraints   are calculated for the scheduling in the Optimizer or liveCache.

There are  two different types of relationships in PP/DS

• Scheduled relationships: In this case, the relationship is scheduled using the factory calendar of resource so that non-working times are considered.
• Non-scheduled relationships: In this case, the relationship is scheduled using the Gregorian calendar so that non-working times are not taken into account.

Wait time – The wait time is always taken into account using a non-scheduled relationship.

Queue times –  the queue time is always taken into account using a scheduled relationship. In this case, the process-related minimum interval corresponds to the minimum queue time, the planning-related minimum interval is defined using the standard queue time.

In the same way as the queue time, the transport time is always taken into account using a scheduled relationship. The process-related minimum interval corresponds to the minimum transportation time; the planning-related minimum interval is defined in the form of the normal move time.

If there is a wait time,  and also a transportation time or queue time defined for an  operation neither the transportation time nor the queue time is taken into account in the relationship duration. The wait time has a higher priority than a transportation time or queue time and therefore only the wait time is ever taken into account as the duration in a relationship.

Considering cross-order (external) relationships

Cross-order as external relationships link activities of different orders like  internal relationships (e.g. between operations defined in a  routing or production order)  and  allow you to define minimum and maximum intervals between linked activities of different orders .

For details refer to  SAP Note “601990 – External relationships (documentation)” and / or “3109069 – External relationships in Advanced Planning (PP/DS) in S/4 HANA (documentation)”

An external relationship between activity A1 in order O1 and activity A2 in order O2 with an “end-start relationship” hierarchy structure category and a minimum interval of zero determines that activity A1 is always to be performed before A2. Such external relationships are considered by the liveCache Scheduler and PP/DS optimization.

In SAP standard cross-order relationships are relevant for subcontracting and the SAP standard system does not include options for setting external relationships explicitly for inhouse manufacturing  or for displaying them.

The main reason for this is that there is no suitable master data that could be used to create external relationships in large numbers.

The SAP note “601990 – External relationships (documentation)” contains a report (“REPORT ZZ_EXT_AOB_CREATE”) that can be used to set external relationships between the activities of two planned orders or production orders.

The report only provides a simple example of how you can create external relationships. It is in no way suitable for use in practice.

Most projects start with the report REPORT ZZ_EXT_AOB_CREATE of note 601990 and customers have to develop an own heuristic from scratch.

In this blog I will show you how you can setup a custom  Service heuristic to accelerate the development of an own solution.

The article   provides also only a simple example of how you can create external relationships. It is also in no way suitable for use in practice. Expect no SAP Standard Support for the function module  e.g. via Service incident.

You can use it to prototype your  function in custom namespace and as starting point / template.

Detailed Scheduling  with Pegging- and Order relationship (Configuration and Business Processes)

In the next section you will find a use case   and how-to guide to setup a production planning scenario that considers fixed  pegging during  scheduling .

Planning and Scheduling scenario with fixed material flow by Pegging

Result of a Planning and Scheduling scenario with fixed material flow by pegging

The picture above shows the result of a planning scenario that plan with exact lot size and considers  no constraints such as  limited capacity or shortage or delay in the material availability.

However, in the daily business constraints and restrictions must be taken into account in real  planning scenarios and thus it is  required to use defined criteria to set fixed pegging relationships between requirements and receipts.

For example, in scheduling during the PP/DS optimizer the production orders have  to be planned as the earliest receipt for upcoming customer requirements and production  orders must  not to be scheduled by the optimizer for later requirements. (e.g. Planned independent requirements)

Following an example of the process flow for delayed dispatching of production orders with SAP standard planning heuristics according to a  Planning and Scheduling scenario without fixed material flow.

Finite planning on Finished Good level with delay to requirements

In the  following infinite planning run (MRP) the net-requirement planning will create replenishment elements (planned orders) on time.

Demand-/Supply situation after net-requirement planning

The planned stock-/requirements result will be repegged dynamically

new dynamic Pegging result

The next finite Planning and Scheduling run  by the PP/DS Optimizer that considers the new pegging relationship will schedule the production order into the future

new finite scheduling result based on dynamic Pegging

To avoid that production orders will be scheduled into the future and the planned date&time on the capacity is filled by  planned orders instead ,  you can control how the Service Heuristic must set the fixed Pegging relationship.  E.g. fixed pegging for production orders and still dynamic pegging for planned orders.

fixed Pegging for Production orders and dynamic Pegging for Planned orders

Finite Planning with fixed Pegging for Production orders

Define in Customizing user-defined heuristic to fixe Pegging relationship according to your own control parameters.

In the next section will find a how-to guide to implement and run  your own defined heuristic with your own control parameters to set up fixed pegging relationship.

The heuristic based on SAP heuristic SAP_PP_019
(Algorithms /SAPAPO/HEU_PEG_FIX_CREATE)

Maintain Heuristic in Customizing IMG

Copy  SAP algorithms to define your own heuristic to fix Pegging relationship.

Transaction: SPRO

Advanced Planning ->   Heuristics -> Maintain Heuristic

On View ‚Change Heuristic‘ mark the SAP Standard Heuristic “SAP_PP_019 Fix Pegging Relationships” and copy it to customer namespace e.g. ‘ZPEG…’

SAP Standard Heuristic in Customizing

On the Screen ‘Heuristic Settings’ enter the following Parameter as selection criteria to fix Pegging-relationships ( example)

For details on User-Defined Settings  refer to the SAP Help: SAP_PP_019 Creation of Fixed Pegging Relationships -> User-Defined Settings

own Service Heuristic as copy of SAP_PP_019

Define Heuristic profile that includes your own new customized   heuristic to fix Pegging relationship.

Transaction: SPRO

Advanced Planning ->  Heuristics -> Maintain Heuristic profiles.

Create for example the following Heuristic profile.

Customized Heuristic Profile

To test the scenario in an PP/DS for SAP S/4HANA System and to call the heuristic from the Product view (transaction /SAPAPO/RRP3) you have to assign the heuristic profile in the User Settings.

Execute Heuristic ‘ZTAA_PP_019 – Fix Pegging Relationship’ from Product View

Product View with Requirements (Forecast) and Receipts (Production and Planned Orders)

Pegging View with dynamic Pegging

Execute own customized Heuristic as Variable Heuristic

Pegging View with dynamic Pegging for Planned orders and fixed Pegging for Production orders.

For fixed pegging the system differentiates between automatically (created by the system/heuristic) and manually created pegging relationships.

The following indicators for the Pegging type  can be displayed:

• D for dynamic pegging relationship

• M for manually fixed pegging relationship

• A for automatically fixed pegging relationship

As result of the Heuristic the Productions orders have a fixed relationship to the demand and a planning run with MRP and Optimization (see scenario above) will not schedule the production orders into the future

Define in user-defined heuristic to  create external (cross-)order relationships.

As described in  PP/DS, the orders from different production stages are connected to each other via “pegging relationships”.

For example, the planned orders can be linked between End Product and Component via Pegging, but it is not possible to specify a minimum or maximum interval between 2 different orders in the PP/DS for SAP S/4HANA standard system.

Without an order relationship between the manufacturing ( production- or planned-) orders, PP/DS can schedule the manufacturing  orders as far apart as you like.

In some Business scenarios it is required  to restrict the min. or max. time period  between the production stages e.g.  mixing and bottling due to the short shelf life of the mixture (as example).

However, orders with a pegging relationship may be a logical unit and should be rescheduled in a coherent manner.

Planning and Scheduling scenario with fixed material flow (w Pegging and Cross-Order relationship)

A function for the automatic creation of external relationships is to be created via a custom  development. External (cross-order)  relationships are necessary in order to take into account the minimum and/or  maximum distance between orders of two levels during optimization.

This means that the following general implementations need to be done:

• Create a heuristic algorithm.
• Customize  the heuristic algorithm via a heuristic ID inclusive all relevant heuristic settings and attributes as well as a proper documentation.
• Ensure that the heuristic can be used in standard PP/DS framework with all the additional benefits offered by the heuristic framework.

The following picture  below shows the situation before the implementation of a Cross-Order-Relationship Heuristic  and the result after the implementation the heuristic when the heuristic has ensured that external constraints have been added to the manufacturing orders.

As shown on scenario 1  orders on the End Product level can be moved from the Component level without any time restriction.

On scenario 2 the orders on the Component level will be “forced” to be finished (by scheduling) latest a defined max. time  before the manufacturing of the End product will start.

The template heuristic  will only create  external / cross-order relationship for orders that are connected to each other via a ” fixed pegging relationships”.

Scheduling of orders w/o external order relationship (min., max.time) and with external order relationship

Define your own heuristic to maintain external (cross-order) relationship.

In the next section you will find a how-to guide to setup your own  heuristics in PP/DS to maintain the external cross-order relationship.

As mentioned at the beginning of the blog the heuristic can be used as template for an own developed heuristic in a project (e.g. developed by a consulting partner or inhouse IT) or as own heuristic to prototype the planning with cross-order / external relationship.

Your own heuristics are an enhancement of the SAP PP/DS  planning processes. Note that even small changes or enhancements to the planning processes can lead to unexpected planning results. Any changes or enhancements you make are at your own risk. SAP cannot be held responsible for any defects or malfunctions resulting from changes or enhancements to the software.

In an integrated system landscape with an ERP system, you should pay particular attention to whether the changes to planning data and orders are also supported by the integration to SAP-ERP.

SAP provides BAdIs for some standard heuristics .  Before you program your own heuristics, check if you can use a BAdI. For more information, see the Implementation Guide for Production Planning and Detailed Scheduling (PP/DS) under Business Add-Ins for PP/DS.

Customizing Heuristic /SAPAPO/HEU_EXT_CONSTRAINTS

Maintain the function module  /SAPAPO/HEU_EXT_CONSTRAINTS in customizing table /SAPAPO/HEURFUNC

PP/DS heuristics in Table /SAPAPO/HEURFUNC

Call transaction SE11 – table /SAPAPO/HEURFUNC

Execute ‚Utilities -> Table Contents -> Create Entries

Enter available heuristic in SAP table /SAPAPO/HEURFUNC

Enter the following data

View for /SAPAPO/HEURFUNC

Maintain the algorithms  as your own heuristic to create/change/delete cross-order relationship.

Transaction: SPRO

Advanced Planning ->  Heuristics ->  Maintain Heuristic

On the Screen ‘Change Heuristic’ execute function ‘New Entries’ and enter the following ( example)

Note

It can be useful in complex planning situations not to consider the maximum intervals so that the system can (more easily) find a solution in detailed scheduling, which can be used as a starting point for further planning.

Customizing heuristic to Delete and Create external order relationship

Enter new heuristic in  to the  Heuristic profile of the previous scenario that includes already your own new customized   heuristic to fix Pegging relationship.

Transaction: SPRO

Advanced Planning ->  Heuristics -> Maintain Heuristic profiles.

Create for example the following Heuristic profile.

Customized Heuristic Profile

As mentioned, the heuristic will only create external / cross-order relationships  for those orders that have already a fixed pegging relationship.

For this scenario you can also fix the pegging relationship between orders  manually in the product view

The Planning  of the heuristic is bottom-up (Default)  according to the Pegging overview in the product view

Fix Pegging relationship Component Receipts to requirements of End product manually and execute Heuristic to create External / Cross-order relationship

Following to the Heuristic run you can check the Min.-& Max.  time interval in the operation  that provides the Component as output to the  component  requirement of the End Product order

Relationships in order detail

The last operation of the order of Component  Product ‘TAA_SFG_10’ has a Min. (1h) and Max.(8h) interval to the order of the End Product  TAA_FG_10 (Order 1929437 Operation 0040 to the first operation 0010 of order 1929421.

With the  heuristics to maintain the fix pegging relationship and  heuristics to maintain the external / cross-order  relationship you can now consider more constraints during Scheduling and Optimization   of PP/DS for SAP S/4HANA and run an end-to-end scenario to optimize the planning and scheduling of your end-to-end bill-of-material.

I hope you enjoyed this blog and gained more insights  about the control  constraints, rules and parameters for Considering Time Relationships  in Scheduling and Optimization of PP/DS for SAP S/4HANA