How to Understand PPDS Production Planning and Scheduling Heuristics

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Executive Summary

  • SNP and PPDS both use heuristics.
  • We cover what are the different heuristics in PPDS and the two heuristics used by SNP.
  • How frequently are the PPDS heuristics implemented versus the optimizer on actual projects?

Introduction: The SNP Heuristic Versus the PPDS Heuristic

As opposed to PPDS, there are just two SNP heuristic. I previously had the SNP heuristic coverage this article but moved to the link below to prevent the article from being too big. You will learn how these heuristics are used.

PPDS Production Scheduling Heuristics

There are two major categories of heuristics in PP/DS. This article will cover the first type, or production planning heuristics. Production scheduling heuristics are covered in this article.

What Are Heuristics Generally?

Heuristics have a general meaning, which is important to understand before moving on to what they mean in SAP. We found a nice definition in Wikipedia that we wanted to list here first.

“Heuristic (pronounced /hjʊˈrɪstɨk/, from the Greek “Εὑρίσκω” for “find” or “discover”) is an adjective for experience-based techniques that help in problem solving, learning and discovery. A heuristic method is particularly used to rapidly come to a solution that is hoped to be close to the best possible answer, or ‘optimal solution’. Heuristics are “rules of thumb”, educated guesses, intuitive judgments or simply common sense. Heuristics as a noun is another name for heuristic methods.

In more precise terms, heuristics stand for strategies using readily accessible, though loosely applicable, information to control problem solving in human beings and machines.”Wikipedia

Heuristics can have many steps or just one step. For instance, there is only one heuristic for SNP to create the network supply plan, but it is multi-step. PP/DS has many heuristics, but may of them be considered single-step. Two that are multi-step emulate MRP. Some things that are very simple and don’t do anything to create the production plan or production scheduled are heuristics in PPDS. One example of this would be

One example of this would be SAP_PP_011 – Delete pegging relationships. This needs to be combined with other heuristics before a production plan can be created.

Heuristics in SAP APO

Heuristics are methods for matching supply and demand. Heuristics exist in both SNP and PPDS. However, in SNP you have the option of running PPDS heuristics. In SCM heuristics schedule infinitely, so they are unconstrained planning. This is the opposite of using the PPDS optimizer optimizes against fixed constraints.

PPDS Heuristics

Specific PP/DS heuristics are available for planning and scheduling. They can be found at the following locations in SCM.

The standard option is “Planning in Planning Run.”

Advanced Planning and Optimization – Supply Chain Planning – Production Planning and Detailed Scheduling – Maintain Planning Procedures

Advanced Planning and Optimization – Supply Chain Planning – Production Planning and Detailed Scheduling – Heuristics – Maintain Heuristics

Heuristic Categories

Heuristics are categorized in APO as either Product (aka lot-sizing procedures), Production Planning Runs (aka process control) or Service Heuristics. The heuristics for each category are listed below.

Product Heuristics

Are further broken down into either Static/Periodic or Optimizing Procedure.
Static, periodic

(these all simply lot sizing heuristics. For instance, the Planning Standard Lots plans products using the lot size in the product master)

  1. SAP_PP_002 – planning standard lots
  2. SAP_PP_003 – plan shortage quantities
  3. SAP_PP_004 – plan standard lots in 3 horizons
  4. SAP_PP_007 – reorder point planning
  5. SAP_PP_C001 – Plan standard lots for county. I/O
  6. SAP_PP_Q001 – quota arrangements

These allow various lot sizes or quotas be the primary planning algorithm.

Optimization procedures

  1. SAP_PP_005 – Part period balancing
  2. SAP_PP_006 – Least unit cost procedure
  3. SAP_PP_013 – Groff procedure

PPDS Production Planning Runs

There is only two Production Planning Runs or Process Control Heuristics, and they mostly emulate MRP. Their only purpose is process control.

  1. SAP_MRP_001 – Production planning (very fast) (applicable for mass applications) (shortage is shown using alerts) This procedure essentially blows out the MRP by the low-level code (or the top item, then the subcomponents and so on). = MRP
  2. SAP_MRP_002 – Product planning does the opposite. It plans all top-level materials and components at once. (aka plan components immediately, if a dependent requirement was created for them in the planning of the superior product).
An interesting result of this is that because MRP is both a supply planning and production planning method,  PPDS can create STRs with an MRP run (which is a PPDS heuristic – SAP_MRP_001). Furthermore, the PPDS Tab has the following “supply planning” deployment “as opposed to the initial supply plan/MPS/S&OP run oriented fields. See the screenshot below:
  1. Fair Share Rule
  2. Pull Deployment Horizon
  3. Push Deployment Horizon
  4. SNP Checking Horizon

Service Heuristics

These do something that matches other heuristics I have worked with in the past.

  • SAP_PP_008 – Rescheduling bottom up
  • SAP_PP_009 – Rescheduling bottom up
  • SAP_PP_010 – Rescheduling top down
  • SAP_PP_019 – Fix pegging relationships
  • SAP_PP_011 – Delete pegging relationships
  • SAP_PP_012 – Change order priorities
  • SAP_PP_018 – Generate safety stock in SAP liveCache
  • SAP_PP_020 – Start numbering algorithm
  • SAP_PP_015 – For deciding which requirements are to be modified and when
  • SAP_PP_014 – Ascertaining PL Ind Requirements: for evaluating any outstanding planned independent requirements.

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Priorities with SAP_PP_012

If you enter priorities in the sales order, these are inherited in the assigned planned order. This may cause problems if you have a planned order with the priority that later in a new situation is linked to another sales order (with a different priority) because the priority in the planned order cannot be changed when the pegging relationships are formed again. For such a situation, you can use service heuristic SAP_PP_012 to adjust the priorities in the planned order to the priorities of the linked sales orders.

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Repetitive Manufacturing in SAP APO

Repetitive manufacturing is designed for the following environments:

  • The same or similar products are made over a long production run (or batch).
  • The production is more of a batch than a specific order.
  • The products produced to follow the same routing and sequence.
  • The routing is simple.
However, the majority of repetitive manufacturing functionality resides on the SAP ERP side which is described in this article. The repetitive manufacturing functionality in PP/DS comes down to the heuristics that are either defined as repetitive, or heuristics that repetitive environments would use. I have both types described in this article. A final repetitive feature is the ability to perform backflushing in APO.

Other Features of Repetitive Manufacturing in APO include

  • Can be used for make to stock production.
  • Backflushing can be performed in APO.
  • Allows for continuous input/output. That is material staging can be distributed over various periods. This is different from discrete where inputs must 100% precede the output. (this is what the SAP_PP_C001 heuristics does) It generates discrete/continual receipts for discrete/continual products.
  • The initial production plan can be run with forward scheduling in any of the methods in SNP. This is described in this article.

Repetitive Manufacturing Production Planning Heuristics

There are two repetitive manufacturing heuristics (called REM heuristics) in PP/DS. According to SAP Help:

Both heuristics create APO planned orders for the existing requirements while taking the available capacity of the resources into account per period. If necessary, you can also define further heuristics for planning the lower BOM levels meaning that you can plan all BOM levels in one planning run. However, planning is only executed for the components which you have defined to be further planned in APO.In this case, APO also creates suitable planned orders for the dependent requirements.

Here are the repetitive manufacturing production planning heuristics as described by SAP.

  • SAP_REM_001 – Multi-resource planning equal
  • SAP_REM_002 – Multi-resource planning primary resource (These are suitable for planning non-configurable products that can be produced on simply structured lines. They carry out a single level individual explosion of the PPM PDS and thus determine the dependent requirements for the BOM level directly below.)

Production Scheduling Heuristics

Most of what is talked about are production planning heuristics. However, there are also standard heuristics just for scheduling, however, there are much fewer of them. While there are roughly 50 heuristics for production planning, there are only six for production scheduling.

Standard Detailed Scheduling Heuristics

  1. SAP001: Sequence scheduling – used to schedule selected operations in a particular sequence in the heuristic settings. You use this heuristic to schedule selected scheduled operations in a particular sequence in the production planning run and in the DS planning board. You specify the scheduling sequence in the heuristic settings. When you start the heuristic for the selected operations, the system deallocates these operations and then schedules them again one after another in the set sequence.
  2. SAP002 – Dissolve backlog – used to reschedule the backlog in the production planning run in the DS planning board, that lie in the past period to the current date or in the future.
  3. SAP003 – Manual sequence scheduling – used to create a scheduling sequence of your choice for a group of selected scheduled operations, sequence of operations is created manually on a graphical list interface when calling up the heuristic.
  4. SAP004 – Lead time reduction – Used to reduce the lead time for orders in the production planning run and in the DS planning board that have operations at selected resource.
  5. SAP005 – Schedule deallocated operations – Use this to reschedule selected scheduled operations

Repetitive Manufacturing Scheduling Heuristic

There are two types of heuristics in PP/DS, those for production planning and those for production scheduling.

  1. SAP_DS_01 – Stable forward scheduling – suitable for the explosion of backlogs or capacity overloads with an unchanged scheduling sequence. The heuristic can be used both interactively in the detailed scheduling planning board and in the background in the production planning run.

Other Heuristics

Block Scheduling Heuristics

  • SAP_CDPBP_01 – Reschedule Blocks
  • SAP_CDPBP_02 – Adjust and Reschedule Block Limits
  • SAP_CDPBP_04 – Block Maintenance, Called Interactively
  • SAP_CDPBP_03 – Enhanced Block Maintenance

Campaign Heuristics

  • SAP_PCM_CRT – Create Production Campaigns
  • SAP_PCM_DIS – Dissolve Production Campaigns

Setup Heuristics

  • SAP_PCM_ODEL – Delete Setup/Clean Out Orders
  • SAP_PCM_SRVA – Create Setup / Clean Out Orders
  • SAP_DS-04 – Activate Sequence Dependent Setup Activities

Independent Requirement Heuristics

  • SAP_PP_014 – Ascertaining PL. Ind. Requirements – Used to determine independent planning requirements that have not yet been matched with sales orders.
  • SAP_PP_015 – Adjust Orders and PL Ind. Requirements – Deletes open planned independent requirements for selected products

Special Order Heuristic

  • SAP_PP_016 – Adjusting Special Orders

Shelf Life Heuristic

  • SAP_PP_SP001 – Planning of standard lots with the shelf life (the same as SAP_PP_002, but takes into account maturation time and shelf life)

Scheduling Agreement Heuristics

  • SAP_CDS_A01 – Admissibility Ok Without Check – This changes the status of all selected sales scheduling agreement items to “admissibility ok.”
  • SAP_CDS_F01 – The quantities and dates requested by the customer are confirmed as matching in the sales scheduling agreements, without a feasibility check.

Tolerance Check Heuristics

  • SAP_CDS_A01 – Tolerance Check
  • SAP_CDS_F02 – Tolerance Check

Days’ Supply Check Heuristics

  • SAP_CDS_F03 – Product Heuristic w. Days’ Supply Check

Standard Lots Heuristics

  • SAP_CDS_F04 – Planning Standard Lots Confirmed Qty

Length Based Material Heuristics

  • SAP_LEN_001 – Used for length based materials, creates new receipt elements to cover product requirements

Co-Product Heuristics

  • SAP_MOP_001 – Multiple Output Planning Heuristic – for co-product items
  • SAP_PP_017 – Planning Standard Lots for Co-Products

Conversion Heuristics

  • SAP_SNP_MULTI – SNP to PP/DS conversion for many products
  • SAP_SNP_SNGL – Individual conversion SNP – PP/DS

Capacity Driven Heuristic

  • SAP_PP_CDOC – Capacity Driven Order Creation

Capable to Promise Heuristic

Capable to Promise is almost never used, and is a bit of a pipe dream, which is explained in this article.

  • SAP_PP_CTP – Planning Shortage Quantities for CTP – Heuristic developed especially for the CTP scenario to allow any subsequent changes to the sales order quantity to be taken into account adequately.
  • SAP_PP_STOWC – Restore Requests f.Contract Release Ords – Restoring of pegging relationships that were automatically fixed between the originating requirement and stock transfer document.

PDS Check Heuristic

  • SAP_CHECK_01 – Check PDS

Forward Scheduling Heuristics

  • SAP_PMAN_002 – Infinite Forward Scheduling – Compact forward scheduling in the event of a scheduling delay in make to engineering or make to order production based on today’s date or an entered date.
  • SAP_DS_01 – Stable Forward Scheduling – used to resolve planning related interruptions using several BOM levels (infinite)

Planning Interval Heuristic

  • SAP_DS_03 – Change Fixed/Planning Intervals

Multi-Level Up or Down Heuristics

  • SAP_MLO_BU – Multi-level, order related, bottom-up
  • SAP_MLO_TD – Multi-level, order related, top-down

Critical Path Heuristic

  • SAP_PMAN_001 – Critical Path – Identification of the critical path in engineering to order or make to order production. Critical path: all operations of an order where a reduction in the operations leads to a reduction in lead time.

Re-explosion Heuristic

  • SAP_PP_021 – Re-Explosion

Miscellaneous

  • SAP_LEN_002 – Manual Creation of LOP Order
  • SAP_MOP_001 – Multiple Output Planning Heuristic

New Heuristics as of APO / SCM 5.1

  • SAP_PMAN_001 = Critical path, identify operations for which there is no float
  • SAP_PMAN_002 = Infinite forward scheduling if the date of the project can no longer be met
  • SAP_PMAN_003 = Infinite backward scheduling
  • SAP_DS_02 = Create and delete fixed planning intervals. The system no longer changes setup times in the short term horizon if the operation sequence has changed because of confirmations.
  • SAP_DS_04 = Reactivate sequence dependent setup activities that lie outside of the planning time fence.
  • SAP_PP_MRPDs = Reads collective orders in ERP and replaces the relationships, which exist between orders, to APO using fixed pegging
Possible to use MRP in SAP ERP, while using detailed scheduling in PP/DS. No transfer of bills of materials.

A full list of heuristics listed on page 469 of SCM250 PPDS

How PPDS is Sold Versus How it is Used

PPDS is often sold as a tool for performing constraint-based planning. However, it is more accurate to say that PPDS can perform constraint-based planning, but this is only in effect if the cost optimizer is used. Quite a few companies have attempted to implement the cost optimizer in PPDS, but very few stay with it, and in my view, the PPDS optimizer is not a sustainable solution.

It should be said that this is not a problem which is unique to PPDS. Optimization in many applications has often run into problems in implementation.

In a forward-looking industry like enterprise software for supply chain planning, there has been a very little analysis of why this has been the case, and very little done to improve implementation methodologies or even slightly adjust strategies on new implementations. For this reason, most of the optimization projects repeat the same mistakes that I first observed on projects back in 1998.

The Limitations at Consulting Companies

Very few consulting companies have the knowledge or ability to socialize optimization solutions with their clients. This is a major reason for the failure of so many optimization projects as is described in this article. The revenue pressures are so high at consulting companies that there is a low ability to communicate the reality to clients on this or other topics.

I have concluded after a good deal of analysis that a primary reason for optimization failure has been the over-application of a single optimization objective function, namely, cost optimization to every supply chain domain. It also should be acknowledged that some vendors have mastered optimization for production planning and scheduling.

The Reality of PPDS

Since the vast majority of companies than implementing PPDS do not use the optimizer (they either use heuristics or no method, simply allowing planners to move jobs around manually to resources), PPDS should be considered an unconstrained tool.

PPDS does have a very wide variety of heuristics, in fact, there are over fifty, which are listed further on in this article. The wide range of heuristics, many directed just towards specific manufacturing environments (for instance, many of PPDS’s heuristics are for repetitive manufacturing) is probably the strongest point for PPDS.

Most PPDS projects result in the PP/DS Consultant matching the combination of heuristics and their sequence to the particular requirements of the production process.

The Problem with Heuristics for Production Planning and Scheduling

Heuristics are a problematic approach to production planning. They provide decent results; they are fast to run, but they are frequently used because they are simple to implement. They also require a lot of manual adjustment. They do however provide a great deal more flexibility than MRP (if we compare them to the production planning heuristics, rather than the scheduling heuristics in PPDS).

Conclusion

The production scheduling heuristics are quite limited compared to the production planning heuristics. This provides insight into the where the focus has been applied from a development perspective with PP/DS. On live implementations, a great deal of scheduling in PP/DS is performed with manual drag and drop.

In fact, some projects do not use any scheduling heuristics at all, and the entire scheduling process is controlled my manual adjustments.

  • To reiterate, the vast majority of PPDS implementations do not use the cost optimizer and are not constrained. In fact, we doubt the ability of PPDS to be taken live at all with the optimizer.
  • I run into clients that think they are performing constraint-based planning when they are running the PPDS heuristics, and this is not correct. SAP consulting, sales and support hides this fact from companies. You can’t get this information from Accenture, IBM, Deloitte or any of the usual suspects. SAP consulting partners normally mislead their clients as to the status of PPDS implementations – repeating false claims made by SAP.

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SAP SNP does not work to constrain resources. It has primarily failures in implementation in both optimization and CTM.

Brightwork Research & Analysis offers the following supply planning tuning software with a new approach to managing capacity constraints, which is free to use in the beginning. See by clicking the image below:

References

Constrained Book

CONSTRAINED

Constrained Supply and Production Planning in SAP APO

How Constrained Supply and Production Planning Works

Constraint-based planning generates something that is appealing to all manufacturers: a feasible supply and production plan. However, constraint-based planning software was first implemented over twenty years ago, and yet few companies (as a percentage that all that have tried) have mastered constraint-based planning.

Getting the Real Story

This book provides the background information, detailed explanations, step-by-step examples, and real-life scenarios to assist a company in becoming proficient at constraint-based planning, along with valuable information about what SAP APO can do for supply and production planning in reality, rather than just in theory. Here you will learn about resources the mechanism for constraining the plan in APO and for determining the feasibility of the plan and how constrained supply and production planning work together (and how they don’t).

Also, this book talks about constraint-based planning at the supplier level: can a vendor’s production be capacity-constrained?

By reading this book, you will learn:

  • The different resources available in APO, how production resources differ from supply planning resources, and the role resources and other significant constraints play in constraint-based planning.
  • How constraints integrate across the supply planning and production planning applications.
  • The areas of disconnect between supply and production planning applications, and between SNP and PP/DS in particular.
  • The difference between unconstrained (or infinite) planning and constraint-based planning.
  • The benefits of constraint-based planning and how it differs from capacity leveling.
  • Various types of demand, and how backward and forwards were scheduling work.
  • The benefits of using production constraints in the supply planning system, and how SNP and PP/DS can be synchronized to produce the desired output.
  • The methods that can do constraint-based planning in SNP and PP/DS–heuristics, CTM, and optimization–and how to configure these methods.
  • The difference between hard and soft constraints, and how to plan using multiple constraints.

Chapters

  • Chapter 1: Introduction
  • Chapter 2: Understanding the Basics of Constraints in Supply and
  • Production Planning Software
  • Chapter 3: Integrating Supply and Production Software with Constraints
  • Chapter 4: Constraint-based Methods in APO
  • Chapter 5: Resources
  • Chapter 6: Capacity-constraining Vendors/Suppliers
  • Chapter 7: The Disconnection Points Between Supply Planning and Production Planning

SCM250 PPDS

https://www.sap.com/spain/company/events/2008_gestion_cadena_logistica/pdf/6_Killer%20Applications%20Day%20SCM%202008_SNP.pdf