Successful business marketing depends on how the information to be maintained, integrated, and extracted from the large scale of data systems. Though CRM, SCM, and ERP are the representative efforts to make relationship between marketing and data, they show low success rates. One of the main reasons is the impetuous processing without enough analysis on the data in order to show the result promptly. Korea Telecom has about 200 information systems that are constructed and maintained separately. Now these independent systems should be integrated as the basis of CRM, SCM, or ERP for the customer-oriented marketing. Constructing a data map that describes the metadata of all information systems and the relationship between systems is the first step of data integration project. We explain the details of the data map and related tool, and describe their effectiveness in this paper.