Time fences are boundaries between different periods in the planning horizon. They define short term regions within which planning restrictions minimize costly disruption to shop floor and supplier schedules.
Time fences also provide guidelines to establish where various restrictions or changes in operating procedures take place. For example, you can easily accomplish changes to the MPS beyond the cumulative lead time while changes inside the cumulative lead time are more difficult to accomplish. Oracle MRP makes use of three time fences: the planning time fence, demand time fence, and release time fence.
You can define planning, demand, and release time fence days for an item based on the cumulative manufacturing lead time, cumulative total lead time, total lead time, or a user-defined value.
You can also use the release time fence to stop the release of Kanban items from Oracle MRP into Oracle Work in Process and Oracle Purchasing.
When you load forecasts and sales orders into a master schedule you can specify whether to use demand time fence control. You can specify whether you load forecasts outside the demand time fence, sales orders within the demand time fence, or ignore demand time fences. See: Selecting Master Schedule Load Options.
When you launch the planning process you can specify whether to consider planning, or demand time fence control. For an MPS plan, you can also choose to overwrite master schedule entries outside the planning time fence. For an MRP plan, you can overwrite all planned orders as well as firm planned orders that fall outside the planning time fence.
Planning Time Fences for Requisitions
Purchase requisitions and internal requisitions are not subject to planning time fence processes.
When you define a plan or schedule name, you can allow the planning process to automatically release planned orders as standard discrete jobs in Oracle Work in Process, or as purchase requisitions in Oracle Purchasing.
You can also use the release time fence to stop the release of Kanban items from Oracle MRP.
Time fence control is a policy or guideline you establish to note where various restrictions or changes in operating procedures take place. For example, you can easily change the master production schedule for an item beyond its cumulative lead time, with little effect on related material and capacity plans. However, changes inside the cumulative lead time cause increasing difficulty, to a point where you should resist such changes because of their effect on other operations. You can use time fences to define these points of policy change. Oracle MRP offers three types of time fences: the demand time fence, planning time fence, and release time fence.
You define demand, planning, and release time fence days when you define an item. You can define the demand, planning, and release time fence for the item as either the cumulative manufacturing lead time, cumulative total lead time, total lead time, or a user-defined time fence.
Oracle MRP defines one boundary of the time fence for an item as the current date, and the other boundary as value of the cumulative manufacturing lead time, cumulative total lead time, total lead time, or a user-defined time.
For example, suppose you define the demand time fence for an item as the cumulative manufacturing lead time and the planning time fence as a user-defined time. The planning process considers the demand time fence (in workdays) of the item as the current date up to the cumulative manufacturing lead time of the item. The planning process considers the planning time fence (in workdays) of the item as the current date up to the time fence value you enter. See: Defining Items, Oracle Inventory User's Guide.
You establish demand and planning time fence control when you set up Oracle MRP. See: Defining Planning Parameters.
You establish release time fence control when you define a plan or schedule name. You can also override time fence control for individual material plans or master schedules when you generate a DRP, MRP or MPS. See: Defining a Schedule Name, and Defining MRP Names.
The demand time fence is bordered by the current date and a date within which the planning process does not consider forecast demand when calculating actual demand. Within the demand time fence, Oracle MRP only considers actual demand. Outside the demand time fence, the planning process considers forecast demand. You can specify whether to use demand time fence control when loading a master schedule and launching the planning process.
The planning time fence is bordered by the current date and a date within which the planning process does not alter the current material plan or master schedule. You can specify whether to use planning time fence control when launching the planning process.
For discrete items within the planning fence, the planning process does not reschedule in (create earlier) order due dates or create new planned orders for the item to satisfy net demand requirements. However, the planning process can reschedule out or cancel an order when it determines that such orders create excess supply. For discrete items outside the planning time fence, the planning process can generate suggestions to create, change, and reduce entries on the master schedule or the material requirements plan.
For repetitive items, Oracle MRP restricts the planning process to suggest rates of production within the planning time fence that differ from the current aggregate repetitive schedule by no more than the acceptable rate increase and acceptable rate decrease you defined for the item. If either the acceptable rate increase or decrease value is undefined, the planning process is not restricted from increasing or decreasing the repetitive schedule respectively.
You can choose whether to display a warning when you define or update MPS entries that violate the planning time fence, or when you define or update MDS entries that violate the demand time fence. Set the MRP:Time Fence Warning profile option to Yes. See: Setting Your Personal User Profile, Oracle Applications User's Guide.
Purchase requisitions and internal requisitions are not subject to planning time fence processes.
The release time fence is bordered by the current date and a date within which the planning process automatically releases planned orders to Oracle Work in Process as discrete jobs or to Oracle Purchasing as purchase requisitions. You can specify whether to use release time fence control when defining your plan name.
The planned orders must meet the following auto-release criteria:
the new due date lies within the auto-release time fence
the lead time is not compressed
the orders are for standard items (will not release models, option classes, and planning items)
the orders are not for Kanban items
the orders are for DRP planned items in a DRP plan, MPS planned items in an MPS plan, or MRP planned items in an MRP plan See: Auto-release Planned Orders.
the release time fence option is defined as anything other than Do not auto-release, Do not release (Kanban), or Null
Auto-release of suggested repetitive schedules is not applicable to repetitively planned items. No material availability check is performed before WIP jobs are released.
A firm order is an order that is frozen in quantity and time (unavailable for rescheduling). Oracle MRP automatically creates a planning time fence for the firm order if the firm order exists after the planning time fence date. There are two methods you can use to firm an order that creates a time fence: you can firm a planned order or firm a discrete job in the Planner Workbench, or you can firm a discrete job or purchase order within Oracle Work in Process and Oracle Purchasing directly.
Oracle MRP creates a time fence for a firm order because it implies that resources committed to meeting the firm order would be unavailable for orders scheduled earlier.
Note: You can use the profile option, MRP: Firm Planned Order Time Fence to indicate whether to form natural time fences for your MRP firm planned orders when launching the planning process.
Oracle MRP does not create a time fence for an MRP firm planned order if you set this profile option to no. See: Setting Your Personal User Profile, Oracle Applications User's Guide.
You can specify the following demand time fence options when you load forecasts into a master schedule.
Load Sales Orders within and Forecast Outside Demand Time Fence
Oracle MRP loads only sales orders on and within the demand time fence and only forecast entries outside the demand time fence
Oracle MRP loads all forecast entries outside the demand time fence and ignores forecast entries on and within the demand time fence. Oracle MRP also loads all sales orders from the start date to the cutoff date if you enter All sales orders in the Include field.
Oracle MRP loads all forecast entries between the start date and the cutoff date and ignores the demand time fence. Oracle MRP also loads all sales orders from the start date to the cutoff date if you enter All sales orders in the Include field.
When you choose to load sales orders into a master schedule, you can manually enter a cutoff date, or use the cutoff date based on the demand time fence. If you use the demand time fence date as the cutoff, Oracle MRP does not consider sales order demand after the demand time fence for an item. If the item has no demand time fence or you ignore the demand time fence, Oracle MRP includes all sales orders up to the cutoff date that you specify. See: Loading a Master Schedule from an Internal Source.
You can specify the following demand time fence options when you load sales orders into a master schedule.
Oracle MRP loads all sales orders within the demand time fence. Oracle MRP does not include sales orders outside the demand time fence.
Oracle MRP loads all sales orders ignoring the demand time fence.
You can specify whether to consider demand and planning time fence control by selecting Demand Time Fence Control and Planning Time Fence Control in the Plan Options window. If demand time fences are active, the planning process ignores entries on the master schedule that have an origination type of Forecast within the demand time fence. This is the same as when you load a forecast into a master schedule and enter Load forecast outside demand time fence only in the Time Fence Option field. You can choose to use either or both methods to eliminate forecasted demand within the demand time fence.
Note: The planning process respects The planning process respects firm orders and the implicit time fences that they create even if you specify not to use Planning Time Fence control. The planning process does not apply Planning Time Fence logic to purchase requisitions or internal requisitions.
When you launch the planning process, you can also choose to overwrite the master production schedule entries and firm planned orders that fall outside the planning time fence for an item.
For an MPS plan, the planning process deletes all master production schedule entries that lie outside the planning time fence, and replaces those entries with a new master production schedule. The planning process does not modify master schedule entries that fall within the planning time fence. You can use this option to induce short-term stability of the master production schedule, while creating the optimal long-term master production schedule.
When you use this option for an MRP or DRP plan, the planning process overwrites all planned orders and firm planned orders outside the planning time fence.
See Also
Overwrite Options.
On-going maintenance of the MPS is critical to the production plan. Your company policies and procedures dictate what changes you can make, when you can make them, and who is authorized to make them.
When you define an item as being MPS planned, you can choose to automatically reduce master production schedule entries. A periodic process (planning manager) automatically reduces master production schedule entries for discrete items based on the option you choose. The planning manager deletes master production entries for repetitive items.
You can use this option to leave master production schedule entries and not automatically reduce them. Production relief decrements the master production schedule entries through the creation of discrete jobs or purchase requisitions.
You can use this option to automatically reduce master production schedule entries as they become past due.
You can use this option to automatically reduce master production schedule entries for discrete items within the demand time fence of the item. (Oracle MRP does not reduce any entries if you do not specify the demand time fence.) Oracle MRP deletes master production entries for repetitive items. This option may be necessary when MPS relief is turned off, or if you are not using Oracle Work in Process. If a master production schedule spans a demand time fence, Oracle MRP truncates it on the time fence date.
You can use this option to automatically reduce master production schedule entries for discrete items within the planning time fence of the item (Oracle MRP does not reduce any entries if you do not specify the planning time fence). Oracle MRP deletes master production entries for repetitive items. This option may be necessary when MPS relief is turned off, or if you are not using Oracle Work in Process. If a master production schedule spans a planning time fence, Oracle MRP truncates it on the time fence date.
See Also
Starting the Planning Manager
For discretely-planned items, the planning process does not recommend that you reschedule in existing orders, and it does not create planned orders, within the planning time fence. However, the planning process can recommend that you reschedule out or cancel existing orders, even if they fall within the planning time fence.
For repetitively-planned items, Oracle MRP restricts the planning process to suggest rates of production within the planning time fence that differ from the current aggregate repetitive schedule by no more than the acceptable rate increase and acceptable rate decrease you defined for the item. If either the acceptable rate increase and decrease value is not entered (null), Oracle MRP is not restricted from increasing or decreasing the repetitive schedule respectively.
Because the planning time fence restricts the actions that Oracle MRP can take, your plan may have material imbalances that require the attention of the master scheduler or planner. You can easily identify those elements of the plan that require the attention of the planner by using the Exceptions window to review action messages. You can view those items and orders based upon a set of predefined exception messages. You can also run the Planning Detail Report or the Supply Chain Planning Detail Report for a specific planner and exception message.
See Also
Reviewing Planning Exceptions Planning Detail Report
The following example illustrates one business scenario that utilizes demand, planning, and release time fences.
Suppose your company builds an item called MODEL. MODEL consists of the following multiple options:
Your company forecasts its material requirements based on MODEL. The company places sales orders demand against predefined configurations that have options OPTION 1, OPTION 2, OPTION 3 as components.
Your company forecasts its material requirements based on MODEL. The company places sales orders demand against predefined configurations that have options OPTION 1, OPTION 2, OPTION 3 as components.
Your company uses a demand time fence. Inside the demand time fence, your company only considers actual sales order demand. Outside the demand time fence, your company only considers forecasted demand. When you load the master schedule from a forecast, you can accomplish this by including all sales orders, and by loading sales orders within and forecast outside demand time fence. See: Loading a Master Schedule From an Internal Source.
In this example, you have defined the demand time fence for MODEL, CONFIG1, and CONFIG2 at period 2. You have not defined a demand time fence for the option items 1, 2 and 3.
The material plan for the item MODEL and one of its options, Option 2, and one of the configurations, CONFIG1, is as follows:
| Period 1 | Period 2 | Period 3 | Period 4 | |
|---|---|---|---|---|
| Forecast Demand | 100 | 100 | ||
| Gross Requirements | 0 | 0 | 100 | 100 |
| MPS | 100 | 100 | ||
| Projected QOH | 0 | 0 | 0 | 0 |
| ATP | 100 | 100 |
| Period 1 | Period 2 | Period 3 | Period 4 | |
|---|---|---|---|---|
| Actual Demand | 50 | 80 | ||
| Gross Requirements | 50 | 80 | 0 | 0 |
| Planned orders | 50 | 80 | ||
| Projected QOH | 50 | 80 | 0 | 0 |
| Period 1 | Period 2 | Period 3 | Period 4 | |
|---|---|---|---|---|
| Demand from MODEL | 50 | 50 | ||
| Demand from CONFIG1 | 50 | 80 | ||
| Gross requirements | 50 | 80 | 50 | 50 |
| Projected QOH | 0 | 0 | 0 | 0 |
Note the following: there is no demand for MODEL in the first two periods since MODEL is not an orderable item it is used primarily for forecast and planning purposes. Demand for MODEL after the demand time fence (period 2) consists entirely of forecasted demand.
Demand for CONFIG1 in the first two periods consists entirely of actual demand. There is no other demand for CONFIG1 because it is not forecasted.
Demand for item OPTION 2 in the first two periods consists entirely of demand passed down from item CONFIG1, which is derived from actual sales order demand for CONFIG1. After the first two periods, the demand for OPTION 2 consists of demand generated from MODEL, which is based entirely on forecasted demand.
You have chosen to master schedule both the model and its options. This results in the production is being driven by sales orders within the demand time fence and by forecasts outside the demand time fence. Oracle MRP derives the master schedule for the options entirely from the master schedule for the model. The options are master scheduled for purposes of order promising. See: Available to Promise.
For this example, you have defined the planning time fence for MODEL as some number of periods out from today, thereby providing stability for the short-term plan. You have not defined a planning time fence for the option items 1, 2, and 3. If you execute the planning process using demand time fence control and you choose to overwrite the outside planning time fence, Oracle MRP overwrites the entire master production schedule for the option items, and creates a new schedule based entirely on actual sales orders for the option items within the demand time fence, and the master production schedule for the model outside the demand time fence.
For this example, your company does not use Oracle Work in Process. Therefore, discrete jobs are not created, and thus never consume the master production schedule for MODEL. To effectively consume the master production schedule for MODEL, you must set the Auto-reduce MPS attribute to Within Demand Time Fence when you define the MODEL item. Whenever a master production schedule entry is within the demand time fence, Oracle MRP automatically reduces it. See: Defining Items, Oracle Inventory User's Guide.
If your company did use Oracle Work in Process and Oracle Purchasing, you could set a release time fence for any planned orders generated by the planning process. If you define OPTION2 with a release time fence of as many days as there are in period 1, then the 50 planned orders for period 1 generated by the planning process would automatically be released. They would be released to Oracle Work in Process as discrete jobs or to Oracle Purchasing as purchase requisition, depending on their item attributes; their job status, requisition load group, and other values would depend on the defaults applicable to the item. With this time fence, the 80 planned orders generated for period 2 would not be released, and would require selection and implementation by the master scheduler or material planner. See: Defining Items, Oracle Inventory User's Guide.