Page 190 - Orlicky's Material Requirements Planning

CHAPTER 9 System Records and Files 169

The Complete Logical Record

In addition to the status-data segment, the item master-data (header) and subsidiary-data
segments make up the item inventory record. All these data together are termed the log-
ical record (data that are logically related) as opposed to the physical record or records
stored in possibly different formats and different locations of computer storage. The data
that constitute a logical record are not necessarily stored together physically. Some of
them may not be stored at all but are re-created in the computer’s main memory for pur-
poses of computation and/or display. This is a matter of programming and the design of
database software that the system user, generally speaking, need not be concerned about.

UPDATING INVENTORY RECORDS

The inventory status data are maintained up to date by means of processing (posting)
inventory transactions against the item inventory record. An inventory transaction is
defined as a notice of an event that changes the inventory status. External inventory
transactions are reported to the system, whereas internal transactions are generated by
the system itself in the course of requirements planning. Reports of certain events that do
not affect inventory status but are posted to the subsidiary data segment of the record are
called pseudotransactions.

Transactions and Other Entries

The status data on which an MRP system depends are maintained up to date by means
of processing transactions against item inventory records. Inventory transactions are not,
however, the only entries processed by the system that affect these records. The several
types of entries that the system processes in order to update inventory records may be
categorized as follows:

1. Inventory transactions
2. User-controlled exceptions to regular processing logic
3. Pseudotransactions
4. Final assembly schedule entries
5. Error-correction entries
6. File-maintenance entries
Inventory transactions act to modify the status of inventory items; that is, status is
changed following the processing of any inventory transaction. A given transaction may
cause subsidiary records to be processed in addition to processing the status-data seg-
ment of the inventory record. A transaction may change the status in such a way as to also
require the updating of component-item status (in net change implementations of MRP
systems), thus affecting multiple inventory records. A transaction may report a normal or
planned event, such as a stock receipt, or an unexpected event, such as a stock return.