|Oracle Manufacturing Scheduling User's Guide|
Part Number E15190-03
This chapter covers the following topics:
When rescheduling jobs you can perform the following tasks:
Reschedule all jobs using forward or backward scheduling.
Reschedule jobs with or without a routing reference. For detailed information, see Rescheduling Discrete Jobs, Oracle Work in Process User's Guide.
Add, update, delete, reschedule, and view operations. For detailed information, see Adding and Updating Operations, Oracle Work in Process User's Guide.
Use midpoint rescheduling to reschedule around a bottleneck job operation. For detailed information, see Midpoint Rescheduling, Oracle Work in Process User's Guide.
Modify discrete job operations, import modified jobs and schedules, and replan planned orders. For detailed information, see Discrete Rescheduling, Oracle Work in Process User's Guide.
Some updates and changes made to jobs automatically launch the reschedule process. This includes changes to:
Start job quantity
Requested Start Date
Requested Due Date
Bill of Material Revision
All other changes such as updates to the job heading, routing, bill of material, require that you manually launch the reschedule process. Refresh the Gantt chart to view these changes.
Note: When Scheduling All or Pending jobs, the scheduling engine does not schedule jobs with past due dates, or jobs outside of the scheduling horizon.
You can access the concurrent program to reschedule all jobs on the shop floor in two ways. You can navigate to the Schedule Discrete Jobs window, or access the Scheduling Parameters window directly from the Workbench. When accessed from the workbench, the workbench passes organization and discrete job information, and you only need to provide two other fields.
Navigate to the Schedule Discrete Jobs window.
The Parameters window appears.
Select an organization.
In the Work Orders field select All Jobs.
The scheduling engine selects jobs with a status of Released, Unreleased, On Hold that are within the scheduling horizon.
In the Scheduling Mode field, select either Forwards from start date or Backwards from completion date.
In the Use Alternate Resources field select either Yes or No. The default is Yes.
In the Work Order Type field, select either Discrete job or Maintenance job.
This field defaults to the type of the organization specified in the Organization field.
Choose OK. The Schedule Discrete Jobs window appears.
See: Submitting a Request, Oracle Applications User's Guide.
A Decision window appears which indicates the request identification number. You can record this number for future reference.
Select Schedule Multiple Work Orders from the Schedule menu.
The Scheduling Parameters window displays.
Select scheduling method in the Scheduling Direction field.
Your choices are Forward from start date, or Backwards from completion date.
In the Use Alternate Resources field, select Yes if you want to consider alternates in the scheduling run, or No if you want current required resources to be used regardless of constraint.
Choose Submit to start the concurrent program.
A Request identifications number displays at the bottom of the Scheduler Workbench. When the program is complete, a confirmation window displays.
When scheduling all jobs, the scheduling engine does not schedule jobs with past due dates, or jobs outside of the scheduling horizon.
In automatic mode, if you grab and drag to the right (forward) or left (backward). beyond the end of the horizon, you will not be able to schedule the job. An error message displays when you choose Schedule on the Automatic Reschedule window, stating that you must either change the schedule date or cancel the transaction.
Defining Work in Process Parameters
Automatically Rescheduling Jobs and Operations
Manufacturing Scheduling supports multiple scheduling methods including backward and forward scheduling at the job level, and midpoint forward scheduling at the operation level.
The Scheduling tab of the Resources window is where you define resource scheduling. The values are Yes, Prior, or Next. If you select Prior, you are including this resource when scheduling the previous operation. If you select Next, you are including this resource when scheduling the next operation. Finite scheduling also considers prior and next operation resources, for example, with fixed setups and teardowns. See: Defining WIP Resource Definition.
Backward and forward scheduling parameters differ depending on whether you are:
Entering scheduling data on the Discrete Jobs window
Rescheduling a single job by dragging and dropping on the Gantt chart
Employing Alternate Resources
The Discrete Jobs window has two areas holding scheduling date information: the Dates region on the main region of the window, and the date fields on the Scheduling tab. These date fields are employed in different ways.
When you initially create a job, you select production dates in the Dates region.
You can forward schedule by specifying a Start date. The constraint-based scheduling engine begins when the record is saved and moves the job forward to the first available time slot as resources and material are available.
You can backward schedule by specifying a Completion date. The constraint-based scheduling engine begins when the record is saved and schedules the job to complete as close as possible to that date. It calculates a production start date, according to resource and material availability.
The values in the Date region may change when the record is saved and scheduling dates are calculated. When the record is saved, these date values and other parameters (such as whether the job has an assembly routing or not, and is standard or non-standard) are used for the date calculation. See: Defining Discrete Jobs Manually, Oracle Work in Process User's Guide. If you are using manufacturing scheduling, the resource and material constraints are used in the date calculations.
The dates on the Scheduling tab are the desired, or target, dates you want for scheduling. When you first create a job, the requested date defaults to date entered in the Date Region. After you select a Requested Start Date or Requested Due Date, the scheduling engine uses that date and scheduling constraints, and attempts to meet the request.
The constraint-based scheduling engine uses the Requested Start Date value to schedule the job from that starting point for forward scheduling, or the Requested Due Date value to schedule the job from that ending point for backward scheduling.
The dates in the Date region may change when the record is saved and scheduling dates are calculated. But the requested dates only change when you manually enter new values.
When you reschedule all jobs on the shop floor from the Scheduler Workbench, the constraint-based scheduling engine considers:
Resources and material
Requested start or due date targets
Job scheduling priority
Note: Firm jobs and any associated operations are not rescheduled.
Scheduling Dates on the Discrete Jobs Window
Defining WIP Scheduling Priority
You can select the primary goal of scheduling. The choice of objective determines the scheduling algorithm used and is used to maximize ontime completion, decrease the number of changeovers, or minimize slack time between job operations. Scheduling algorithms use penalty factors and machine and resource setup models. The scheduling objective is defined in the WIP Parameters window. See: Defining Work in Process Parameters, and Setting Up Scheduling Objectives.
Note: When jobs on the shop floor have varying scheduling priorities, scheduling logic looks at jobs having the same priority when determining the order operations selected for scheduling. The group of jobs with the highest priority is scheduled first, then the next highest priority group is scheduled next, until all jobs are scheduled.
Maximize Ontime Completion
This scheduling objective employs only backward scheduling and incorporates penalty calculations including due date, inventory carrying, setup, and operation slack. See: Penalty Factors. When this objective is used, the algorithm uses the following logic:
The last operation of every job on the shop floor, having the same priority level, is evaluated for penalty factor time totals.
The cumulative penalty factor of all the jobs is calculated. The job operation with the highest penalty is scheduled first and allocated resources.
Then, the last operation, or next to last operation in the job already scheduled, is evaluated again for penalty factor times.
The cumulative penalty factor for this next set of last job operations is calculated. The job operation with the highest penalty is scheduled next and allocated resources.
The system evaluates all the job operation sets until the last operation is scheduled on the shop floor.
This scheduling objective employs both backward and forward scheduling. Machine and resource setup changeovers, and transition penalty factors are used in the scheduling calculations. See: Defining Resource Setup Information. When this objective is used, the algorithm uses the following logic:
The system evaluates all resources used for jobs on the shop floor with setups and changeovers, and calculates the transition penalties.
It then reviews all the operations using this resource, totals all penalty factors, and selects the operation with the highest penalty aggregate.
The operation selected is scheduled first.
Then system again evaluates all resources used for jobs with setups and changeovers, and calculates the transition penalties.
It then reviews the remaining operations, not scheduled, using this resource; totals all penalty factors, and selects the operation with the highest penalty aggregate.
The operation selected is scheduled next.
The evaluation and scheduling continues until all operations are scheduled.
Minimize Operation Slack
This scheduling objective employs both backward and forward scheduling. It incorporates calculations including due date, inventory carrying, setup, and operation slack. See: Penalty Factors. When this objective is used, the algorithm uses the following logic:
The penalty factor time for each job on the shop floor, having the same priority level, is calculated.
The job with the highest penalty aggregate is scheduled first and allocated resources. If it is backward scheduled, the scheduling begins at the last operation of the job. If forward scheduled, the scheduling begins at the first operation of the job. All the operations in the job selected are scheduled.
Next, the penalty factors for the remaining jobs on the shop floor are calculated.
The next job with the highest penalty aggregate is scheduled first and allocated resources. All the operations in the job selected are scheduled.
The system evaluates all the jobs on the shop floor until the last job is scheduled.
Rescheduling a single job or operation on the Gantt chart using constraint-based scheduling uses the same scheduling logic as finite scheduling. The scheduling attempts to meet the due date of the job or operation, setups are sequenced, and slack is minimized. The difference in rescheduling a single job or operation is that no other jobs or operations are moved, this can effect your objectives. Start or end dates can be rescheduled both manually and automatically. You can:
Midpoint and midpoint forward schedule at a selected operation
Backward schedule from a previous operation
Schedule an operation using the midpoint or midpoint forward scheduling method
The Automatic Reschedule window enables you to specify the start and end dates, forward or backward schedule a job, and schedule an operation using the midpoint or midpoint forward scheduling method. The required resource and material are used as the determining factor.
Select Automatic Scheduling from the menu or toolbar, and use the pointer to automatically forward or backward reschedule a job.You can forward schedule by selecting the right of the job or operation bar. Or backward schedule by selecting the left of the job or operation bar.
The constraint-based scheduling engine uses the selected date or searches for the first available time slot as resources and material are available. The job's operations and resources move with the job.
See: Automatically Rescheduling Jobs and Operations
You can forward or backward schedule using the pointer or the Edit Schedule window, enabling you to manually reschedule any job, operation, or resource without regard for constraints or scheduling rules.
You can forward schedule by selecting the right of the job, operation, or resource. Or backward schedule by o the left of the job, operation, or resource.
Or you can use the Edit Schedule window to enter new start or end dates for the required job or operation. The required resource and material are used as the determining factor.
See: Manually Rescheduling Start and End Dates
Alternate resource functionality only employs backward scheduling, because alternate resources do not use start dates:
When rescheduling single jobs, the alternate resource is invoked if the primary resource does not enable the job to complete by the Requested Due Date. It will revert back to the primary resource if neither the primary or alternate resource can complete by the date.
When rescheduling multiple jobs, the scheduling logic looks at the Job Priority, Requested Due Date, and Completion Date values. The alternate resource is invoked if the primary cannot complete by the due date. If neither primary or alternate resource can meet the date, the primary resource is used.
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