Page 184 - Orlicky's Material Requirements Planning

C HAP TE R 9

System Records and Files

After all, the engineers create the bill so that, by definition, somebody other
than the designer can make the product. The bill of material is, therefore, really
made for others in the first place. And it would seem to follow that it should be
structured for the user’s, not the designer’s, convenience.
—GEORGE W. PLOSSL, IN MRP AND BILL OF MATERIAL STRUCTURE,
FILM PRODUCED BY INTERNATIONAL BUSINESS MACHINES CORP., 1972

A material requirements planning (MRP) system can be thought of as a set of logically
linked item inventory records coupled with a program (or programs) that maintains
these records up to date. The design of the inventory record, as well as the way the data
it contains are being manipulated to produce valid system outputs, is crucial to both the
effectiveness of the system and an understanding of the subject of MRP.

THE TIME-PHASED RECORD

Under the MRP approach, a separate time-phased inventory record is established and
maintained for every inventory item. Each record consists of three portions, or segments,
as follows:
1. Item master data (record header)
2. Inventory status data (the body of the record)
3. Subsidiary data

The inventory status segment is either reconstructed periodically or kept up to date
continuously depending on which of the two basic alternatives of implementing an MRP
system—schedule regeneration or net change (discussed in Chapter 7)—had been cho-

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