Page 191 - Orlicky's Material Requirements Planning

170 PART 2 Concepts

While both may have the same physical effect, the regular processing logic must be mod-
ified (as will be shown later) to register unexpected events.
User-controlled exceptions to regular processing logic represent another category of
entries processed against inventory records. Such entries serve as a means of intercession
by the inventory planner. In certain situations, human judgment is required to evaluate
and solve a problem, and the planner must be able to override the system’s regular logic.
In this category belong several types of commands that the MRP system can be pro-
grammed to obey. One example is a hold command to prevent a (mature) planned order
from being issued, perhaps because of a contemplated substitution in raw material.
Another example is a scrap-tag command that tells the system not to call for release of a
new order if its quantity is smaller than the scrap allowance of an existing open order. A
firm planned-order command, which freezes a planned order in place, is another exam-
ple. The use of this command was discussed in Chapter 8.
Pseudotransactions are entries to the subsidiary-data segment of the item inventory
record. Pseudotransactions do not affect inventory status. Examples are a purchase-req-
uisition issue (status will be affected only on the release of the purchase order) and a
change in an open-order detail. Another example is the recording of a subcontractor’s
work authorization. These transactions do not affect inventory, but they do have a sig-
nificant financial impact. Final-assembly-schedule entries apply to highest-level items
only in those cases where the end products themselves (because of their complexity) do
not appear in the MPS. When the final assembly schedule, which is stated in terms of
product models, is put together, the high-level components on which it will draw may be
allocated in the respective inventory records. In another type of manufacturing business,
a customer order may be processed this way on receipt. In an assembly-line environment,
a day’s or week’s final production may be broken down into high-level components con-
sumed, summarized by component, and processed against the respective component
inventory records in lieu of stock-disbursement transactions, which are not otherwise
reported for highest-level items.
Error-correction entries are not genuine transactions because they do not affect real
status. In some MRP systems, special transaction codes are used to distinguish error-cor-
rection entries from genuine transactions that have the same effect. For example, the
inventory planner releases an order for item A but erroneously reports it as item B. In the
record of B, there now appears an open order. The error is corrected by processing an
entry that reverses the previous transaction rather than by an order-cancellation transac-
tion. The effect would be the same, but the distinction is made for purposes of record.
File-maintenance entries affect the item master-data segment (header) of the item
inventory record. Such entries update the record for changes in the attributes of the item,
for example, standard cost, classification, item description, and so on, or for changes in
planning factors such as lead time or scrap allowance. File-maintenance entries do not
affect inventory status, or rather, their processing does not trigger the replanning process
in standard implementations of MRP.