The purpose of a Data Warehouse is to give power/enough data/KPIs to leadership to make high level business decisions.
This is achieved by the following:
1) Generating daily/weekly/monthly reports for C –level executive decision making.
2) Generating KPIs, scorecards for visual representation of historical/real-time data.
Data Warehouses are typically huge repositories/volumes of data gathered from multiple source systems. Implementing data warehouses requires huge investments of money with the end result/value addition achieved by management not fully known at the beginning of the project.
Data Migration Projects
Data Migration projects are executed for moving data from one/multiple source systems to a target system. There is well defined end result out of executing data migration projects. Hence, business will be very much inclined to invest money in executing Data Migration projects. This could be needed from a business perspective for one of the following reasons:
1) Source system consolidation may happen. Multiple source systems might be merged into one.
2) In a SAP ERP scenario, multiple ERP instances could be merged into a single instance to cut TCO (Total Cost of Ownership).
3) Some source systems may become redundant/deprecated. Hence, those systems data has to be merged with another/new source system.
4) Data could be migrated across database vendors, for example, from SQL Server to Oracle.
5) Data migration from lower version to higher version say from Oracle 9i to Oracle 11g or from SAP ECC 4.6c to ECC 6.0.