I would like to know how to prepare a data mapping document for ETL process. In order to prepare data mapping document, one has to know the source and target database. I have seen data mapping documents prepared in Excel.Are there special tools such as ETL software Informatica or others that are used in creating data mapping document?. Is it automated or manual effort in creating this?. Please let me know where to start. I might soon be asked to work on this , but not quiet sure of the best approaches.Thanks in advance.