1. Using Maintenance
  2. How Maintenance Work Orders are Scheduled

How Maintenance Work Orders are Scheduled

Oracle Maintenance uses unconstrained scheduling engine in the background to schedule work orders during create and certain update actions. In addition, the scheduling engine is also used to compute the manufacturing lead time of a product based on its primary work definition.

The scheduling engine uses the information provided at the resource definition, work order operation resource level and the resource's calendar to determine the resource's start date and completion date for in-house operations. While scheduling work orders, resources are assumed to have infinite capacity and the scheduling engine disregards loads on the resources from other work orders. It rolls up the resource dates to determine the start and completion dates of each in-house operation. For supplier operations, the scheduling engine uses the lead time information specified at the operation level to calculate the start and completion date of the operation. Eventually the operation dates are rolled up to determine the work order dates. The required date of the operation items are updated to the start date of its operation. The following types of scheduling methods are supported by the scheduling engine:

  • Forward Scheduling

  • Backward Scheduling

  • Midpoint Scheduling

Forward Scheduling: When a work order is forward scheduled, the scheduling engine uses the start date of the work order as an input to determine the start and completion dates for each scheduled resource (for in-house operations), the start and completion dates for each operation and eventually the completion date of the work order. The application automatically performs forward scheduling when the start date of a work order is provided. Forward scheduling is also used by the lead time calculation program to determine the manufacturing lead time of the product.

Backward Scheduling: When a work order is backward scheduled, the scheduling engine uses the completion date of the work order as an input to determine the start and completion dates for each scheduled resource (for in-house operations), the start and completion dates for each operation and eventually the start date of the work order. The application automatically performs backward scheduling when the completion date of a work order is provided.

Midpoint Scheduling: When a work order is midpoint scheduled, the user selects an operation to perform midpoint scheduling by specifying either the operation start date or the operation completion date. If Midpoint scheduling is performed from the operation start date, all the prior operations are backward scheduled while the selected operation and succeeding operations are forward scheduled. If Midpoint scheduling is performed from the operation completion date, all resources of the prior operations and the selected operation are backward scheduled while the succeeding operations are forward scheduled.

The following actions trigger scheduling or rescheduling of work orders:

  • Create Work Orders: When work definition is specified, application automatically performs either forward or backward scheduling depending on whether start date or completion date is provided.

  • Update Work Order - Start Date or Completion Date: Updating one of these date nulls out the other and application automatically performs either forward or backward scheduling.

  • Update Work Order - Work Definition name or Work Definition Date or Work Order Quantity: Updating any of these fields on the work order triggers the application to prompt forward scheduling or backward scheduling method to reschedule the work order.

The following attributes influence the scheduling behavior:

  • Work Order Start Date or Completion Date: Serves as the anchor point to perform forward or backward scheduling.

  • Work Order Operation Start Date or Completion Date: Serves as the anchor point to perform midpoint scheduling.

  • Work Order Operation Resources Sequence Number: Resources which have unique sequence numbers within an operation are scheduled sequentially in the ascending order. Resources which share a common sequence number within an operation are considered as simultaneous resources and are scheduled in parallel. However, in the case of released work orders with resequenceable operations, the execution sequence will be considered instead of the operation sequence.

  • Work Order Operation Resources Name: Used by the scheduling engine to determine the work center resource calendar to schedule the resources.

  • Work Order Operation Resources - Required Usage: Used by the scheduling engine to schedule the resource duration.

  • Work Order Operation Resources - UOM: Used by the scheduling engine to schedule the resource duration. The resource usage is converted from the specified unit of measure to the scheduling unit of measure using the profile Hour Unit of Measure. The UOM set in this profile must belong to the UOM class specified in the other profile SCM Common: Default Service Duration Class (RCS_DEFAULT_UOM_CLASS_CODE_FOR_SVC_DURATION). For any scheduled resource, it's recommended that this profile be set to a UOM class that represents units of measure for Time.

  • Work Order Operation Resources - Scheduled Indicator: Resources which have Scheduled = Yes are considered by the scheduling engine to compute the duration of the resource. The resources which have Scheduled = No aren't scheduled and assumed to have the zero duration, such as start date = completion date.

  • Work Order Operation Resources - Assigned Units: The required usage of the resource is divided by the assigned units to compute the scheduled duration of the resource.

  • Work Center Resources - Available 24 Hours Indicator: Resources which have this indicator set to No are scheduled within the shifts associated with it. Resources which have this indicator set to Yes, are assumed to be available 24 hours.

  • Work Center Resources - Efficiency and Utilization Percentages: The scheduling engine inflates the required usage of a resource if its efficiency and, or utilization percentages are less than 100%.

  • Work Center Resources - Shift Assignments: Scheduling engine considers the availability of resources based on the shifts assigned to the work center resource.

  • Work Center Resource Availability: Scheduling engine considers the shift exceptions and work center resource exceptions to determine the availability of resources within shifts assigned to it.

  • Supplier Operation Lead Time Attributes: For supplier operations the scheduling engine uses the Fixed Lead Time, Variable Lead Time, and Lead Time UOM information provided at the operation level to calculate the start and completion dates of the operation.