A closer look at Data under the IDEA tool-bar will reveal a function 'Append' - Fields.
'Append' under Fields in Data allows you to append or add fields to the active database.
You may need to add fields to perform calculations or reassess values in the accounting system or derive values/strings or add comments - limitless possibilities.
On the other hand 'Append' under 'Relate' in Analysis allows you to merge databases into a single file for further analysis.
This is particularly useful when you receive a single report in parts from an accounting system for better load balancing on the system. 'Append' under 'Relate' in Analysis can be used to merge the smaller files into one larger file for further analysis.