Migrating Data to an Integrated Database - High-Performance Web Databases: Design, Development, and Deployment - page 606

Exhibit 42-7. Representing an algorithm to detect value inconsistencies.
values, or some other automatic calculation to derive a single target value.
These approaches are not recommended because they do not improve the
accuracy of the data.
On the other hand, some database administrators retain both values in
the database to let the end user choose which value to use. This method is
not recommended either because it puts the burden on the individual
using the data, instead of the individual entering the data.
It is recommended that the owner of the data refer back to the original
source to determine the accurate value of the data. However, this can be an
expensive and time-consuming activity. The database administrator
should consider how to balance the cost of obtaining accurate data with
the cost of mistakes due to inaccurate data to determine how much effort
should be expended to correct known database errors.
A completely accurate database may be very expensive to maintain
because of the cost of validating each data item. However, this may be nec-
essary for databases that may have serious implications when their users
take inappropriate actions based on inaccurate or out-of-date data. For
example, errors in a police warrant database or a pharmacy's drug interac-
tion database may result in loss of life, but errors in a holiday card mailing
list or a television broadcast schedule are not life-threatening.
DATA MIGRATION TOOLS AND SERVICES
Many tools are available for migrating data from a source database to a
target database. Generally, data migration tools assist the database admin-
istrator in constructing scripts that: