Time Fences, Schedule Stability and Change Control

Introduction

Master production scheduling (MPS) converts aggregate production intentions into time-phased commitments for specific end items. Its value depends not only on creating a feasible schedule, but also on controlling how and when that schedule may change. A schedule that changes repeatedly can be mathematically feasible at each revision and still be operationally ineffective. Production teams lose setup sequence discipline, suppliers receive contradictory signals, materials are expedited, labour plans become unreliable, and customers experience avoidable delays.

Time fences provide a governance structure for this problem. They divide the planning horizon into zones with different rules for changing orders. The most common zones are the frozen, slushy and liquid zones. These zones are supported by demand and planning time fences, firm planned orders, approval procedures and exception-based rescheduling.

Schedule stability does not mean that the schedule must never change. It means that changes are made deliberately, transparently and at an economically justified frequency. The central managerial task is to balance responsiveness against stability.

Learning Objectives

By the end of this chapter, the reader should be able to:

• explain the purpose of time fences in an MPS;
• distinguish frozen, slushy and liquid planning zones;
• differentiate demand time fences from planning time fences;
• describe firm planned orders and schedule-freezing policies;
• measure schedule nervousness and interpret its operational meaning;
• evaluate the cost, service and capacity consequences of schedule changes;
• design a change-control process using priorities, approvals and exception rules;
• apply time-fence logic to a practical production-management problem.

1. The Need for Schedule Stability

An MPS normally contains planned production quantities by item and period. Let M_i,t denote the planned quantity of item i in period t. In practice, this quantity is influenced by forecasts, customer orders, inventory, lot-sizing rules, capacity, material availability and existing commitments.

A schedule change occurs when a later MPS revision changes the quantity, timing or status of an order. Typical changes include:

• moving an order to an earlier or later period;
• increasing or decreasing its quantity;
• cancelling an order;
• changing an order from planned to firm;
• replacing one product configuration with another;
• changing the production sequence within a period.

Some changes are beneficial. A customer may place a high-margin order, a critical component may become unavailable, or a safety issue may require an immediate engineering revision. Other changes are caused by weak forecasting, inaccurate inventory records, poor data discipline or excessive managerial intervention.

The term schedule nervousness describes undesirable instability in planned orders or production dates caused by repeated planning revisions. Nervousness is not measured merely by the number of changes. A single large change may be more disruptive than several small changes, and a change near the production date is generally more costly than an early change.

Schedule stability produces several benefits:

1. Operational predictability: supervisors can arrange labour, tooling, materials and maintenance.
2. Lower transaction costs: planners spend less time reworking orders and communicating corrections.
3. Improved supplier coordination: suppliers receive credible dates and quantities.
4. Better quality and productivity: stable sequences reduce rushed setups and errors.
5. Higher employee confidence: production personnel are less likely to disregard the MPS as unreliable.
6. Improved customer service: promised dates are based on a schedule that the plant can realistically execute.

Stability, however, has an opportunity cost. A completely rigid schedule may fail to respond to urgent demand, shortages, engineering changes or profitable market opportunities. Effective control therefore requires differentiated rules rather than universal rigidity.

2. Time-Fence Logic

A time fence is a boundary in the planning horizon beyond which a defined change policy applies. The horizon is usually expressed in weeks, days or manufacturing periods measured from the current date.

2.1 Frozen, slushy and liquid zones

The three-zone model is a practical framework for graduated control.

The exact boundaries should reflect the operating environment. A make-to-stock plant with short lead times may freeze only a few days. A project-oriented manufacturer with long-lead components may require a frozen horizon of several months.

Frozen zone

The frozen zone contains orders that are considered operational commitments. The quantity, timing and often the sequence are protected. A planner may not alter them simply because a forecast has changed.

A change may be authorised when it is necessary to protect safety, legal compliance, a strategic customer, a critical service commitment or the viability of the plant. Approval normally comes from a cross-functional authority such as the master scheduler, production manager, materials manager and sales or customer-service representative.

Freezing is not identical to physically starting production. An order can be frozen while still awaiting release, provided the organisation has committed to its planned execution.

Slushy zone

The slushy zone permits controlled adjustment. Changes may be accepted if they satisfy conditions such as available capacity, material feasibility, minimum production quantities, customer priority or a defined economic threshold. The zone prevents every minor forecast revision from entering the shop floor while preserving some responsiveness.

Typical controls include:

• a maximum number of allowed changes per item and period;
• a weekly or daily review of proposed changes;
• restrictions on changing quantities by more than a specified percentage;
• approval when a change affects suppliers, overtime or customer promises;
• a requirement that the planner record the reason and expected benefit.

Liquid zone

The liquid zone is the least committed part of the horizon. Forecasts are uncertain, capacity plans may still be adjusted and material orders may not yet be placed. MPS quantities can generally be changed to reflect updated demand and planning assumptions.

Liquid does not mean irrelevant. A large change in the liquid zone may affect aggregate capacity, supplier forecasts or future inventory. It should therefore remain visible through exception reports and capacity review.

3. Demand and Planning Time Fences

Two related but distinct fences are commonly used in MPS and material-requirements planning.

3.1 Demand time fence

The demand time fence (DTF) separates near-term demand that is largely known from demand that is primarily forecast. Within the DTF, customer orders may be treated as the dominant demand signal. Forecast changes may be ignored, limited or offset through management review.

For example, if the DTF is two weeks, the MPS may use actual sales orders for the next two weeks and a combination of orders and forecast beyond that point. The DTF protects the schedule from replacing known requirements with speculative revisions.

The DTF is principally a demand-management concept. It does not by itself determine whether production orders may be changed.

3.2 Planning time fence

The planning time fence (PTF) identifies the period within which the MPS is sufficiently committed that the planning system should not automatically create or modify orders using ordinary planning logic. Within the PTF, planned orders may be converted to firm planned orders or may require manual approval before revision.

The PTF is principally a supply and execution-control concept. It reflects lead times, capacity commitments, purchasing actions and shop-floor readiness.

The two fences may be equal, but they need not be. A company may know demand accurately for four weeks while requiring six weeks of production commitment because of long material lead times. Conversely, a company may have a long customer-order visibility window but retain production flexibility because components are common and capacity is ample.

3.3 Selecting fence lengths

Fence lengths should be based on operational facts rather than arbitrary calendar conventions. Relevant considerations include:

• cumulative manufacturing and procurement lead time;
• time required to procure constrained or custom materials;
• setup and changeover characteristics;
• capacity flexibility and labour availability;
• supplier reliability;
• customer promise policies;
• product postponement opportunities;
• forecast accuracy by horizon;
• cost of expediting, cancellation and obsolescence.

A useful principle is that the frozen horizon should cover the period in which significant resources have become difficult or expensive to redeploy. It need not equal the total product lead time if late-stage postponement or flexible capacity is available.

4. Firm Planned Orders and Status Control

A planned order is a system-generated proposal for future production. It may be changed by subsequent planning runs as demand, inventory or supply assumptions change. A firm planned order is a protected planning commitment. It communicates that the quantity and date have been reviewed and should not be automatically altered.

Firming is a governance decision, not merely a software setting. An order should normally be firmed when:

• materials have been allocated or purchased;
• labour or a production slot has been reserved;
• the order lies within the planning time fence;
• the customer promise depends on the order;
• the planner has validated capacity and component availability.

Firming too early creates rigidity, excess inventory and obsolete production. Firming too late causes avoidable disruption and unreliable customer promises. The appropriate point depends on the cost and reversibility of commitment.

A useful status sequence is:

1. forecast or demand signal;
2. planned order;
3. firm planned order;
4. released production order;
5. operation in progress;
6. completed or closed order.

Each transition should have a responsible owner and defined evidence. For example, release may require material availability, a valid bill of materials, an approved routing and adequate capacity.

5. Schedule-Freezing Policies

A schedule-freezing policy specifies what may change, who may authorise it and how its effects are evaluated. A sound policy contains at least six elements.

5.1 Scope

The policy should identify products, plants, production lines, customers and planning horizons covered by the rules. A single policy may not suit both high-volume repetitive production and engineered-to-order production.

5.2 Change categories

Changes should be classified rather than treated as a single event. Common categories are:

• quantity increase or decrease;
• date advancement or delay;
• cancellation;
• product substitution or configuration change;
• sequence change;
• material or routing change;
• emergency release.

5.3 Authority matrix

An authority matrix assigns approval rights. For example, a planner may adjust a liquid-zone order, the master scheduler may approve a slushy-zone change, and a steering group may authorise a frozen-zone exception affecting a strategic customer or constrained line.

5.4 Impact assessment

Before approval, the planner should examine material availability, capacity loading, setup effects, supplier commitments, customer service, inventory and financial consequences. The analysis should distinguish direct cost from downstream disruption.

5.5 Communication and traceability

Every approved change should have a reason code, requester, approver, date, old value, new value and affected functions. Traceability supports learning and prevents disputes about which version is authoritative.

5.6 Performance review

The organisation should review not only whether changes were approved, but also whether the resulting benefits materialised. Frequent emergency changes may indicate an incorrect fence, weak forecasting, inaccurate master data or unrealistic promised dates.

6. Measuring Schedule Nervousness

No single metric captures all forms of instability. Measurement should combine frequency, magnitude, timing and consequence.

6.1 Quantity-change measure

For item i and period t, let M_i,t^(r) be the MPS quantity in revision r. A simple absolute change between two consecutive revisions is:

The unit is the item quantity. This measure is useful for identifying large changes but cannot distinguish a change of ten units in a ten-unit order from ten units in a thousand-unit order.

A relative change, when the previous quantity is nonzero, is:

It is dimensionless and often expressed as a percentage. When the previous quantity is zero, the ratio is undefined; the analyst should report the absolute change or use a denominator such as the average of the two quantities, with an explicit policy.

6.2 Weighted instability index

To reflect the greater impact of late changes, assign a weight w_t to each period. Let c_i,t be the unit consequence cost of changing item i in period t. A weighted index can be defined as:

This is an organisation-specific management index, not a universal accounting identity. The weights and consequence costs must be defined consistently. For example, w_t may increase as the period approaches execution, while c_i,t may include setup, expediting and service effects.

6.3 Date instability

For an order with planned completion date d^(r), date movement can be measured as:

The unit is days or weeks. Separate reporting should identify advances and delays because their consequences differ. A delay may threaten customer service, whereas an advance may create inventory or overtime.

6.4 Nervousness dashboard

A useful dashboard includes:

• percentage of frozen orders changed;
• number of changes per order before release;
• average and maximum date movement;
• quantity changes by zone;
• emergency changes by reason code;
• schedule adherence to the frozen MPS;
• customer promise performance;
• overtime, premium freight and material-expediting cost;
• cancellations and obsolete inventory.

Metrics should be segmented by product family, planner, facility, customer class and horizon. Aggregate averages can conceal serious instability in a particular line.

7. Evaluating the Consequences of Change

A proposed schedule change should be evaluated as a portfolio of consequences rather than by its immediate demand benefit alone.

Cost consequences

Direct cost may include overtime, premium freight, additional setup, subcontracting, cancellation charges and inventory carrying cost. Indirect cost includes lost productivity, disrupted supplier schedules, rework and managerial time.

If inventory carrying cost is estimated using annual holding-rate h, unit value v, and average incremental inventory I, the annual carrying-cost approximation is:

Here h is expressed as a decimal per year, v as currency per unit and I as units. The result is currency per year. The approximation assumes the incremental inventory remains present for the relevant average period and that the holding rate represents the applicable annual cost.

For a shorter period of n days in a year of D days, a simple prorated estimate is:

This is appropriate only when the holding rate is treated as a linear time-based approximation.

Service consequences

A change may improve service for one customer while damaging another. Evaluation should consider promised-date adherence, fill rate, order lateness, allocation fairness and strategic-account commitments. A customer priority rule should be explicit; otherwise urgent requests can become an informal and inequitable queue.

Operational consequences

Operational effects include sequence-dependent setup, line imbalance, labour displacement, maintenance conflicts, component shortages and increased probability of quality problems. A schedule change that appears feasible in aggregate capacity may be infeasible at a particular work centre or shift.

Capacity and material feasibility

The planner should test whether the revised schedule satisfies both material and capacity constraints. In simplified form, capacity feasibility for work centre k in period t requires:

where a_i,k is the capacity requirement per unit of item i at work centre k, in machine-hours or labour-hours per unit, and C_k,t is available capacity in the same hours for the period. The expression is necessary but not sufficient: sequence, lot-size, setup, skills and material availability may impose additional constraints.

8. Change-Control Process

A disciplined process can be implemented as follows.

Step 1: Identify the trigger. Record whether the request arises from a customer order, forecast revision, shortage, engineering change, quality issue, equipment failure or management decision.

Step 2: Locate the order in the time-fence structure. Determine whether it is frozen, slushy or liquid and whether it is firmed or released.

Step 3: Establish the baseline. Capture the current quantity, date, status, sequence, material allocations and customer promise.

Step 4: Generate alternatives. Alternatives may include partial production, substitution, postponement, overtime, split delivery, rescheduling a different order or rejecting the request.

Step 5: Evaluate impacts. Test capacity, materials, inventory, customer service, supplier effects, cost and quality risk.

Step 6: Apply authority rules. Route the proposal to the required approver. Emergency approval should not eliminate documentation.

Step 7: Communicate one valid schedule. Update the MPS, ERP/MRP records, shop-floor dispatch information, supplier signals and customer commitments consistently.

Step 8: Review the outcome. Compare expected and actual effects and investigate repeated exceptions.

This process should be supported by version control. Employees must be able to identify the current authorised schedule and distinguish it from prior revisions.

9. Worked Example: Measuring and Evaluating a Change

An illustrative manufacturer produces two products, A and B. The next three weekly MPS revisions for product A are shown below.

Between revisions 1 and 2, absolute quantity changes are 20, 20 and 20 units, giving a total absolute movement of 60 units. Between revisions 2 and 3, the changes are 0, 30 and 30 units, giving a total of 60 units again. The equal totals do not imply equal disruption: the second revision changes week 2 and week 3 in opposite directions, potentially creating two sequence and material effects.

Suppose week 1 is frozen, week 2 is slushy and week 3 is liquid. The revision from 100 to 120 in week 1 is a frozen-zone change and requires approval. The change from 60 to 90 in week 2 is a slushy-zone change and requires impact assessment. The change from 140 to 110 in week 3 is normally permitted, subject to aggregate capacity review.

Assume the week-1 increase requires 20 additional units, each consuming 0.5 machine-hours, while only 6 additional hours are available. Required additional capacity is:

The request therefore exceeds available overtime capacity by 4 hours. Alternatives include moving part of the increase to week 2, using an alternate work centre, subcontracting or declining the change. The example shows why a frozen-zone change cannot be approved solely because demand exists.

10. Illustrative Case: Meridian Pumps

Background

Meridian Pumps, a fictional industrial-pump manufacturer, operates a five-day production week. Its products use common motors but product-specific impellers and testing routines. Customer demand is variable, and the sales department frequently requests schedule advances near the promised date.

Problem

The plant used a two-week frozen horizon but allowed sales managers to alter frozen orders through informal email requests. During one quarter, 28% of frozen orders were changed. Overtime increased, suppliers received conflicting requirements and on-time delivery fell from 94% to 87%. Planners also reported that supervisors stopped trusting the MPS and began maintaining local spreadsheets.

Analysis

A cross-functional team classified the changes. Forty percent were caused by genuine equipment or quality emergencies, 35% by customer-requested advances and 25% by forecast revisions. Most forecast-driven changes had little commercial benefit but caused setup disruption. The team also found that the demand time fence and planning time fence were both set at two weeks despite a three-week lead time for a critical impeller.

The plant estimated the following effects:

• frozen-zone change: average direct and indirect disruption cost of 420 currency units per order;
• slushy-zone change: 160 currency units per order;
• liquid-zone change: 35 currency units per order;
• premium freight and overtime were not included in these averages and were tracked separately.

Approach and solution

Meridian introduced a four-week planning time fence and retained a two-week demand time fence. The first two weeks became frozen for quantity and completion date; weeks three and four became slushy. Orders were firmed when impellers were allocated or when the order entered the four-week planning fence.

A change board met twice weekly. Frozen changes required approval from production, materials and customer service. Emergency changes required a reason code and a post-event review. Sales could request changes but could not authorise them unilaterally.

The plant also introduced a “protect the bottleneck” rule. A customer advance was accepted only when the constrained test station had capacity or when an alternative order could be moved without damaging a committed promise.

Outcome

After three months, the proportion of frozen orders changed fell to 9%. On-time delivery recovered to 93%, and premium freight decreased. Some sales managers initially viewed the policy as inflexible, but customer service improved because promised dates became more credible. The team also discovered that several apparent emergencies were actually caused by inaccurate inventory records and late engineering releases.

Learning points

The case illustrates five principles:

1. Time fences must reflect material and capacity lead times.
2. A demand fence and a planning fence answer different questions.
3. Emergency flexibility requires governance, not unrestricted access.
4. Schedule stability improves when data accuracy and release discipline improve.
5. The objective is not minimum change; it is economically justified change with reliable execution.

11. Technology, Analytics and Contemporary Practice

Modern ERP, advanced planning and scheduling systems can enforce time fences, firm orders, approval workflows and version histories. Planning engines can compare alternative schedules against capacity and material constraints. However, automation does not eliminate the need for managerial judgement. An algorithm may recommend a schedule change that is technically feasible but commercially inappropriate or operationally disruptive.

Analytics can identify recurring causes of nervousness. For example, machine-learning models may classify likely emergency changes using demand volatility, supplier reliability, equipment condition and order characteristics. Such models should support, not replace, accountable decision-making. Users need explanations of the factors driving a recommendation, and planners must be able to override a model when safety, quality or customer commitments justify doing so.

Digital integration also creates governance risks. If sales, production and suppliers access different versions of the schedule, apparent instability may be caused by communication failure rather than planning logic. Access permissions, audit trails, master-data ownership and cybersecurity are therefore part of schedule control.

Contemporary practice increasingly combines frozen commitments with postponement. Companies keep common components in flexible form and delay final configuration until demand becomes clearer. This reduces the cost of forecast error while preserving customer responsiveness. The effectiveness of postponement depends on product architecture, quality requirements, skilled labour and the economics of late differentiation.

12. Limitations and Critical Considerations

Time fences are not universally beneficial. Excessively long frozen zones can create inventory, obsolete products and missed sales. Excessively short frozen zones can create chaos and undermine supplier relationships. Fixed fence lengths may also be inappropriate when demand volatility differs substantially among products.

A further limitation is that schedule stability metrics can be gamed. If managers measure only changes inside the frozen zone, planners may move instability to the boundary or avoid firming orders. If they measure only quantity changes, date movements and sequence disruptions may be hidden. Balanced measurement is essential.

Another issue is fairness. When capacity is scarce, a change-control policy should define how competing customers are prioritised. Possible principles include contractual commitment, safety or regulatory importance, economic contribution, urgency and strategic relationship. The selected principle should be transparent and consistent with company policy and applicable law.

Finally, stability should not become resistance to learning. If actual production repeatedly differs from the MPS, the response should not be merely to freeze more periods. Management should investigate forecast bias, inaccurate bills of material, unrealistic standards, poor maintenance, supplier unreliability and weak process capability.

Best-Practice Checklist

• Define DTF and PTF separately and document their purposes.
• Set fence lengths using lead time, uncertainty and reversibility of commitment.
• Protect frozen orders through approval controls and firm planned orders.
• Permit liquid-zone changes while reviewing their aggregate capacity effects.
• Record old and new values, reason codes, approvers and consequences.
• Measure quantity, date, frequency and economic impact of changes.
• Use exception management rather than constant manual intervention.
• Include suppliers, customer service, production and finance in material changes.
• Review repeated exceptions as evidence of structural problems.
• Align ERP settings, shop-floor dispatching and customer communication.

Chapter Summary

Time fences govern how much flexibility is permitted as an MPS moves closer to execution. The frozen zone protects near-term commitments, the slushy zone permits controlled adjustment, and the liquid zone remains relatively flexible. Demand time fences distinguish known near-term demand from forecast demand, whereas planning time fences protect supply and execution commitments. They should be designed separately when demand visibility and operational lead times differ.

Firm planned orders convert proposals into protected planning commitments, but firming too early or too late creates different forms of risk. A schedule-freezing policy should define change categories, authority, impact assessment, communication, traceability and review. Schedule nervousness can be measured through absolute and relative quantity changes, date movement and weighted indices that reflect timing and consequence.

A change should be evaluated across cost, customer service, capacity, materials, quality and fairness. Technology can strengthen control through workflows, analytics and version management, but it cannot replace accountable judgement. The managerial objective is not absolute rigidity; it is a stable, feasible and economically responsive schedule.

Key Terms

Time fence: A boundary that determines the rules governing schedule changes.

Frozen zone: The near-term planning period in which changes require formal approval.

Slushy zone: An intermediate period in which limited, controlled changes are permitted.

Liquid zone: The distant period in which schedule changes are normally allowed.

Demand time fence: A boundary separating relatively known demand from forecast-dependent demand.

Planning time fence: A boundary protecting supply and production commitments from routine replanning.

Firm planned order: A planned order protected from automatic system revision.

Schedule nervousness: Undesirable instability caused by repeated changes to planned orders or dates.

Schedule stability: The ability to execute a plan without frequent disruptive revisions.

Change control: The formal process for requesting, evaluating, approving and communicating schedule changes.

Reason code: A classification explaining why a schedule change occurred.

Exception management: Managing unusual events without repeatedly altering normal planning rules.

Frozen-zone breach: An unauthorised or approved change to a protected near-term order.

Capacity feasibility: The condition that required work-centre capacity does not exceed available capacity.

Postponement: Delaying final product differentiation until demand information improves.

Schedule adherence: The extent to which actual execution follows the authorised schedule.

Version control: Identification and preservation of the current and prior schedule revisions.

Emergency change: A change justified by an urgent safety, quality, customer or operational condition.

Review Questions

Short Answer Questions

1. What is the principal purpose of a time fence in an MPS?
2. How does a demand time fence differ from a planning time fence?
3. Define a firm planned order.
4. Why can a completely rigid schedule be undesirable?
5. Name four indicators that can be used to measure schedule nervousness.

Long Answer Questions

1. Explain the characteristics and managerial policies of frozen, slushy and liquid zones.
2. Discuss the factors that should be considered when setting planning and demand time fences.
3. Explain how schedule changes create cost, service and operational consequences.
4. Design a schedule-freezing policy for a make-to-order manufacturer with long-lead components.
5. Evaluate the role and limitations of ERP and advanced planning systems in schedule change control.

Analytical / Application Questions

1. A plant has a two-week frozen zone, a three-week slushy zone and a six-week total planning horizon. A customer requests an advance for an order currently scheduled in the frozen zone. Construct a change-control analysis identifying the information, alternatives and approvals required.
2. An MPS quantity changes from 200 to 240 units in one revision and from 240 to 180 units in the next. Calculate the absolute changes and relative changes for both revisions, and explain why the second revision may be operationally more disruptive.
3. A work centre has 80 available hours in a period. Product X requires 0.5 hours per unit and Product Y requires 1.5 hours per unit. The proposed schedule contains 100 units of X and 20 units of Y. Determine whether the aggregate capacity constraint is satisfied, then identify at least two additional feasibility checks that remain necessary.

Multiple Choice Questions with Answers

Question 1

Which zone normally permits changes only through formal approval?

A. Frozen zone

B. Slushy zone

C. Liquid zone

D. Postponement zone

Correct Answer: A. Frozen zone

Question 2

A demand time fence primarily separates:

A. Capacity from labour

B. Known demand from forecast-dependent demand

C. Raw materials from finished goods

D. Suppliers from customers

Correct Answer: B. Known demand from forecast-dependent demand

Question 3

What is the main purpose of a firm planned order?

A. To permit automatic rescheduling

B. To protect a reviewed planning commitment

C. To eliminate capacity checks

D. To replace the bill of materials

Correct Answer: B. To protect a reviewed planning commitment

Question 4

If an MPS quantity changes from 100 to 130 units, the absolute quantity change is:

A. 30 units

B. 100 units

C. 130 units

D. 230 units

Correct Answer: A. 30 units

Question 5

Which factor most directly supports a longer frozen horizon?

A. Very short and flexible material lead times

B. Long lead times for constrained components

C. Perfect forecast accuracy

D. Unlimited capacity

Correct Answer: B. Long lead times for constrained components

Question 6

In the capacity expression ∑ᵢ aᵢ,ₖ Mᵢ,ₜ ≤ Cₖ,ₜ, what does Cₖ,ₜ represent?

A. Customer demand

B. Unit selling price

C. Available capacity at work centre k in period t

D. Inventory policy

Correct Answer: C. Available capacity at work centre k in period t

Question 7

Why should late schedule changes generally receive greater attention in a nervousness index?

A. They are always smaller

B. They are closer to execution and harder to reverse

C. They never affect suppliers

D. They automatically improve service

Correct Answer: B. They are closer to execution and harder to reverse

Question 8

Which item should normally be recorded for an approved schedule change?

A. Only the new quantity

B. Only the requester's name

C. The old value, new value, reason and approver

D. Only the customer’s industry

Correct Answer: C. The old value, new value, reason and approver

Question 9

A planning time fence is principally concerned with protecting:

A. Supply and production commitments

B. Advertising expenditure

C. Product colour preferences

D. Annual financial statements

Correct Answer: A. Supply and production commitments

Question 10

Postponement improves responsiveness mainly by:

A. Eliminating all forecasts

B. Delaying final differentiation until demand is clearer

C. Freezing the entire planning horizon

D. Increasing every setup frequency

Correct Answer: B. Delaying final differentiation until demand is clearer