Reference data files contain system reference tables and codes, for example, a customer file, VAT code file, or address file. The files are relatively small; their contents are relatively constant over time (they are "non-volatile"), and many programs usually refer to the files in the system.
Do not mix reference and transaction summary data in the same file. The two types of data have different activity levels. Except when actually being maintained, usage of reference files should be "read only".
Where the applicability of a reference file record is time dependent, for example, for a currency or a price rate, cancellation of a record should be recorded via an "active date", or an "inactive date", not by a marker. Users will rarely cancel a record at the precise time at which it becomes inactive. Consider an "active date" to permit items to be entered in advance of their availability for processing.
Consider, where appropriate, providing an indication that the code defined by a record has been referenced by a transaction. This helps to preserve the referential integrity of the database: a record in use may not be deleted. Users may however create "provisional" records that are subsequently never referenced, and may be purged.
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