Information Technology Reference
In-Depth Information
enhancements because such enhancement requests are well anticipated.
Certain design choices today can help in a better migration tomorrow:
Avoidance of the use of features in the underlying technology that
are unique, or are major extensions to what can be generally
expected in other implementations of that technology. Obviously,
if the technology has been selected because these extended fea-
tures are essential for the application, then the designer must make
use of them.
Incorporation of features related to making future data migrations
easier, for example, an ODBC (open database connectivity) bridge
or an object-relational mapping tool. Many migration projects get
into trouble when it comes to data migration.
General modular architectures that make the migration less mono-
lithic and allow a phased migration.
Use of standards (e.g., IETF [Internet Engineering Task Force])
instead of developing proprietary protocols that may make the
migration effort considerably involved.
It is difficult to make a call on what the destination platforms will be
for a future migration. However, certain design improvements can help
that process and will be appreciated by those doing the migration many
years later.
Migrating Data
Bringing data from the old to the new system can be either simple or
very complex. Hence, the effort must be scoped properly. Even if the
data model changes are minimal, there may be attributes and configuration
parameters, such as RDBMS page size, number of database connections,
access control granularity, or page locking, that need to be set differently
in the target system. If the data models are substantially different, then
the mapping effort can be considerable.
How much data should be brought across? The obvious answer is: all
data that was being kept online in the source system because it could
still be required in the target system.
What about archived data in the source system? One needs to decide
if one wants to discard it, or also migrate it. There is little advantage in
retaining it in the old format because one will not be able to access it
once the “old” application has gone away. Migrating all the old data may
not be feasible, or worth the effort. Sometimes it may make sense to walk
away from old data in the new system while preserving the data (in some
