Controlling Detailed Scheduling

Alongside the desired scheduling date, the basis of detailed scheduling for an order, for example, are the capacity requirements of the activities. You control which constraints, rules, and parameters the system must take into account during scheduling using settings and data in the following objects:

Dates/Times and Planning Directions

The starting point for scheduling or rescheduling is the desired start or end date/time of the orders or operations. When you create an order, for example, the availability date/time of the primary order product defines the desired end date/time. If you reschedule an operation on the detailed scheduling planning board using Drag&Drop, for example, the desired date/time is the date/time at which you “let go” the operation.

Starting from the desired date/time, the system searches for a scheduling date/time in the set planning direction for the last activity (backward planning direction) or for the first activity (forward planning direction) of an operation or an order. If the first activity is scheduled, it is then the turn of the next activity in the sequence, and so on until all activities of the operation or order are scheduled or rescheduled. The system cannot schedule or reschedule an activity before or after the application-dependent earliest possible or latest possible date/time.

Resource Availability

The date/time at which an activity can be scheduled or rescheduled on a resource depends on the capacity requirement of the activity and on the working times and capacity of the resource. In general, you can only process activities during the working times of a resource, and you can therefore only schedule these activities in regular working times. In working times, you can schedule activities finitely or infinitely, that is, with or without taking the resource capacity and the existing resource load into account. If necessary, you can also schedule activities during non-working times, such as breaks. Scheduling during a downtime  due to a machine breakdown or maintenance, for example  is not possible. Activities that take longer than one continuous working time may have to be interruptible by non-working times in order to be capable of being scheduled.

Selection of Resources

In the PPM for an activity, you can enter several alternative sets of resources (modes) on which the activity can be performed. Mode selection can be automatic or manual (in the latter case, on the detailed scheduling planning board).

Time Relationships

Time relationships may exist between activities, regulating which minimum and maximum time intervals they can have. The system always takes the mandatory end-start relationships between the activities of an operation into account. If you have entered a minimum interval of one hour between two activities of an operation, for example, the system is not allowed to schedule or reschedule these activities in such a way that the time interval is undercut. You specify in the detailed planning strategy whether the system is to take time relationships between activities of different operations into account when scheduling.

Pegging Relationships

Pegging relationships can exist between the activities of different orders. In this case, an activity produces a material that then undergoes further processing through an activity of another order. The pegging relationship requires — within a certain tolerance — that the material be available at the right time (meaning that the supplying activity must be scheduled in good time). You specify in the detailed scheduling strategy whether the system should consider pegging relationships during scheduling.

Automatic Propagation of Changes

When you schedule or reschedule an operation or an order, other operations and orders are affected. In order for the schedule to remain consistent, subsequent rescheduling is often necessary. This can be performed automatically by the system.

Determining the Setup Time for Sequence-Dependent Setup Activities

The duration of the setup activity for an operation can depend upon the setup status of the resource at the time of scheduling, that is, upon which operation was processed at the resource before. For setup activities on single resources, the system can automatically determine the correct setup times during detailed scheduling.

Synchronizing Activities on Multiresources

Several activities can be processed simultaneously on multiresources. How many can be processed depends on the resource consumption of the activities and the capacity of the multiresource. The system can synchronize the start times of activities during detailed scheduling if the activities match up in terms of their duration and one other characteristic.

Block Planning

In block planning, you can define blocks for resources. These are time segments that are reserved for the production of products with certain characteristics. The system automatically takes this into account during detailed scheduling and only schedules or reschedules activities into the blocks with suitable characteristics.

Scheduling Log

In the scheduling log, the system collects messages that it generates in interactive planning or in the production planning run during scheduling. You can call the scheduling log:

Terminating Scheduling

In complex scheduling situations, in which many constraints and dependencies must be considered, the duration of scheduling can be very long. The system is set internally to terminate scheduling after approximately 10 minutes. You can set a different maximum scheduling duration in the detailed scheduling strategy.

Alerts

In the case of scheduling problems (for example, resource overload), the system can generate alerts, which it displays in the Alert Monitor. You must use a corresponding PP/DS alert profile for this purpose.