Exploring Concepts and Principles of Detailed Scheduling

The goods receipt time is copied from the SAP S/4HANA material master to the SAP PP/DS product master. Note that the scheduling of goods issue and goods receipt times is carried out using the handling resources stored in the location. Calendar resources (infinite resources with 24-hour operating time) should be defined as handling resources. If goods receipt processes are to be planned finitely, then it would be most appropriate to model this using a suitable process in PDS (and not using the goods issue time).

Which basic settings are relevant during detailed scheduling?

• Resource: Available capacity, rate of capacity utilization, parallel loading by several activities (multi-activity resources), and so on

• PDS: Activity duration, interruption of activities, minimum and maximum allowed time intervals between activities, and so on

• Heuristic and strategy: Planning with finite or infinite scheduling

During detailed scheduling, the system determines the start and end dates for the activities of orders or operations and schedules the orders and operations at the resources. Capacity availability in specific contexts can be taken into account directly in this case. In addition to the desired availability date of the operation or order, detailed scheduling is based on the durations and capacity requirements of the activities that the system calculates when the production data structure is exploded.

In addition to the resource consumption and activity duration (defined for each base quantity of the primary product), you can also specify in the PDS whether time relationships exist between the activities of different operations, how large the minimum and maximum time intervals are between the activities, or whether activities can be interrupted by non-working times (breaks), for example.

In the resource, you can specify the working and non-working times, rate of capacity utilization for the resource, whether the resource can only process one activity at a time (single-activity resource), whether the resource can be occupied by several activities at the same time (multi-activity resource), and whether the resource is to be scheduled finitely or infinitely in capacity planning.

You use the detailed scheduling strategy to determine how the system executes scheduling or rescheduling. For the PP heuristics, the strategy is usually defined in the heuristic settings.

What is determined in the detailed scheduling strategy?

• Finite or infinite scheduling

• Forward/backward scheduling with and without reversal

• Find gaps (finite scheduling)

• Insert or squeeze an operation

• Form a scheduling sequence

• Consideration of order-internal relationships

• Consideration of pegging relationships

• Scheduling in Non-Working Times

You use the detailed scheduling strategy to specify which rules the system uses to schedule or reschedule orders and operations on resources, and which scheduling constraints (for example, product and resource availability) should be considered. Note that other operations may be affected when an operation is scheduled or rescheduled.

Use the detailed scheduling strategy to determine:

• Whether finite scheduling is to take place (in other words, the capacity load caused by operations that were already scheduled is taken into account on finite resources)

• The planning direction (in which direction, starting from the desired date, the system begins the search for a scheduling date)

• The offset time (the time interval by the earliest possible start date for scheduling an activity can deviate from the current date or the current time)

• Whether the system searches for a gap during scheduling (so that an operation is scheduled into the first gap in the planning direction with sufficient capacity)

• Whether an operation is to be inserted (so that an operation in an existing plan is scheduled as close to the desired date as possible)

• Whether scheduling takes place in non-working times (whether operations are to be scheduled manually in non-working times – this is only relevant for the planning board)

• The scheduling sequence (in which sequence operations or orders for an operation group or order group are to be scheduled)

• Whether order-internal relationships are to be considered (whether the relationships and time constraints between activities and operations are to be considered)

• Whether pegging relationships are to be considered (whether fixed and dynamic pegging relationships between orders are to be considered)

You can use the Find Slot finite scheduling mode to schedule an operation in the first slot in the planning direction that is long enough and has enough available capacity. You can only use this scheduling mode for resources that are to be finitely scheduled. In the scheduling parameters for the resource, you specify whether a resource is finite or infinite. In the case of infinite resources, the system always schedules an operation infinitely on the desired availability date, that is, without taking existing schedules into account.

If you want to allow an operation to start in the past in the schedule, you can use the offset time in the strategy profile. To do this, specify a negative offset time.

The offset time can be entered as positive or negative. With a positive time, you can only permit scheduling after a certain time frame as of today.

You can use the Insert Operation finite scheduling mode to schedule an operation in an existing schedule on (or as close as possible to) the desired date, even if there is no slot in the schedule for this date, or only a slot that is too small. If necessary, the system generates a gap that is big enough by moving the neighboring operations on the resource in the planning direction specified in the strategy. The sequence of the scheduled operations is therefore not changed. The changes are automatically implemented in the complete collective order.

You can only use this scheduling mode for single resources to be planned using finite scheduling.

The planning direction you set determines the "insert operation" date. If an operation is already scheduled on the desired date, the operation to be inserted is inserted according to the planning direction immediately after (forward planning direction) or before (backward planning direction) the operation that has already been inserted. The operations already scheduled are moved further according to the planning direction.

If the system cannot find a gap big enough, for example, because this would violate relationships, all operations remain where they are and the operation is not inserted.

You can use the Squeezing in an Operation finite scheduling mode to schedule an operation in an existing schedule on (or as close as possible to) the desired date, even when there is no slot in the schedule for this date, or only a slot that is too small. If necessary, the system generates a gap that is big enough by moving the neighboring operations on the resource in both directions.

You can only use this scheduling mode for single activity resources to be planned finitely.

In the DS planning board, working times are shown in white, regular non-working times in gray (breaks, weekends), and downtimes (machine shutdowns) in dark gray.

• You can show and hide non-working times in the DS planning board.

• You cannot show and hide downtimes in the DS planning board. You cannot schedule operations in downtimes.

Scheduling in non-working times is controlled in the strategy profile. The system only permits scheduling of the operation on this date when all other prerequisites have been fulfilled (for example, no constraints have been violated by scheduling).

The system fixes the operations that you schedule in non-working times, in other words, the operations can no longer be rescheduled. Even when you undo the non-working times indicator, the operations remain fixed. To reschedule operations again, you must first undo the fixing.

This scheduling mode is available in the Expert View and the DS View of the strategy profile. You can use Infinite Scheduling for single-activity and multi-activity resources.

Dependent operations are scheduled infinitely and independent of the settings that you have configured in the strategy profile.

Do not use infinite sequencing if you use operations with sequence-dependent setup activities, as this may lead to unexpected planning results (for example, that a schedule without gaps is not possible for the rescheduled operations).

If resources are going to be planned using finite scheduling in some applications and using infinite scheduling in others, you can use the finiteness level function.

You can define the finiteness level in the Customizing settings for the resource or in the global settings in PP/DS. The specified value indicates the limit up to which resources (also) behave finitely and after which they (only) behave infinitely from the application's point of view (heuristic, strategy profile, optimization profile). Conversely, the entry in each application defines the maximum finiteness level up to which the resources used are to be planned using finite scheduling.

The finiteness level of each resource is defined in the master data of that resource. The default value of 0 in the resource (or no finiteness level maintained) means that the resource in question is to be treated as finite in all applications. For this reason, the system assigns the finiteness level 0 to all existing resources for which the Finite Scheduling indicator is set. In this case, the system sets the relevant entry in the application (for example, the strategy) to 9999.

When alternative modes are used, the following prerequisites must be fulfilled before switching to alternative resources:

In the PDS, you have stored more than one mode with alternative resources for each activity of an operation. The activity can be executed on these resources. You have assigned the same priority to linked modes.

Alternatives are generally not the same. You might prefer to operate a fast, expensive special machine to full capacity rather than the slower, cheap alternative machine. You should therefore assign priorities to the modes. Priority A represents the highest priority. Assign priority Z to modes that you want to exclusively plan manually in the detailed scheduling planning board.

When creating an order, the system selects the mode automatically according to priority and availability date. In the detailed scheduling planning board, you select the mode manually.

If you deselect an activity mode (for example, mode 1 on the slide) during rescheduling by dragging and dropping, the other activities of the same mode are also deselected.

In PDS, the mode linkage is defined using mode linkage types in the relationships. The following link types are available:

• Linkage between modes with the same mode names: You can only use this linkage type for linking activities of different operations. Relationships must also be created and assigned to linkage type 3 (Same mode number).

• Linkage between modes that have the same primary resource. This linkage type is obligatory for the linkage between two activities of an operation. However, it can also be used for linking activities that belong to different operations. Relationships must also be created and assigned to linkage type 2 (Identical primary resource).

In PDS, the mode linkage must be set using a BAdI or SAP S/4HANA transaction PDS_MAINT.