Migrating Data to an Integrated Database - High-Performance Web Databases: Design, Development, and Deployment - page 605

Exhibit 42-6. Combining two source data elements to create a single target.
integrated database, these applications cannot be executed. Database
administrators should validate that the data in the source file is not needed
in the target file.
Database administrators should also pay special attention to data in the
target file that is not present in the source file. This data represents new
database requirements and may indicate that an expensive data collection
effort may be necessary to populate the new data item, so applications
accessing the new data can be executed.
VALUE INCONSISTENCIES
Whenever there are two independent sources of values for a data item, it
is possible that the values may be inconsistent. Exhibit 7 includes an algo-
rithm for detecting such inconsistencies. It is assumed that the first source
of values has already been migrated to the target Vehicle file. Exhibit 7 also
illustrates the pseudocode for detecting inconsistencies between records of
the source Truck file and the target Vehicle file. If there is no matching Vehi-
cle record for the Truck record, then a new Vehicle record should be created
and values should be moved into the corresponding data elements of the
Vehicle record. However, if there is a matching Vehicle record for the Truck
record, then the values of the corresponding elements should be compared.
If an inconsistency is detected, the error should be reported right away so
that the inconsistency can be corrected manually.
When inconsistencies occur, some database administrators calculate
the maximum of the values, the minimum of the values, the average of the