One of the first tasks your migration team should agree upon to execute a smooth migration process is the migration strategy. Considering the migration project requirements, the timeframe for completion, and various other factors, you can decide to go with either an iterative approach or a big bang approach.
In this approach, the data warehouse is migrated in small increments over time, on a per-subject area basis. Each subject area consists of integrating the data sources needed to fulfill the analytic requirements (e.g., reports /dashboards) of a specific business area like Sales or Marketing.
If you have a Kimball style data model, the iterative approach fits very well, and you can map to the different data marts that serve a specific subject area.
Top reasons for choosing a staged approach:
- Showing value to end users very early by migrating data marts which suffer most from problem such as performance
- As part of your data warehouse modernization strategy, you can change the ETL tool or BI reporting tool
- Each iteration is a learning opportunity and improves the migration of the next subject area
As the name suggests, big bang migration involves migrating your entire data warehouse in one go.
Top reasons for choosing a Big bang approach:
- Having a highly integrated data model which makes it difficult to split the migration into smaller iterations
- To eliminate the costs of your legacy vendor, you must migrate before a contract renewal
- During the assessment phase, you have concluded that the migration has low risks and no significant obstacles. This might be the case if, for example, you don’t have to migrate a lot of SQL statements with Teradata specific syntax