Find 'em, Fix 'em / Find/Fix/Data conversion and bridge programs

#### Access-driven data conversion

With this design, records are converted only when accessed. This spreads the conversions over time and converts only the records that are being used. At some point, unconverted records may be archived or deleted rather than converted. This works well when the retention period is finite and only a subset of records are accessed.

This diagram shows a re-write design, but in-place updates can be done if the dates are being compressed or if the dates can be expanded within variable-length records. The access program first tries to retrieve and process a record from the converted data store. If it is not found, the access program retrieves the record from the original data store, converts it, processes it, stores it into the converted data store, and deletes it from the original data store.

One use of the design would be a credit-card company with a significant number of card holders with infrequent use. Performance should improve over time.