Data migration or data integration is the data warehouse concept of moving data from one data source to another. This may involve moving data from an AS400 system to and Oracle database or moving data from and Oracle database into a SQL Server database. The distance between the source and destination databases is not normally an issue as long as a connection between the two can be established.
The migration is normally performed using data integration software (otherwise known as an ETL tool) such as Informatica or Business Objects Data Integrator. It may however, also be done using hand crafted code. However, this is
a time consuming option, and often one which is difficult to maintain and support long term. This aspect is important to bear in mind when considering a data integration strategy.
Instances where a company may need to perform a migration exercise include companies moving from a legacy database platform to another, or perhaps if they merge with another company and have a need to bring their systems together.
In order to perform a successful migration, data from the old source system needs to be ‘mapped’ to the new system. This is known as a ‘data mapping’ exercise. This may also involve an intermediary step when some form of calculation or function is applied to the data. This is normally a good time to perform a data cleansing exercise.
Once the data has been transferred into the new system, a period of testing should be undertaken to ensure that the data was transferred and loaded as expected. Only once this has been
completed, can the old data be archived and the old system turned off.