When you import a Microsoft Azure Blob Storage Source object, the Data Integration Service creates a FileName port in the imported data object. The FileName port stores the name of the file from which the Data Integration Service reads the data at run-time.
For example, a directory contains a number of files and each file contains multiple records that you want to read. You select the directory as source type in the Microsoft Azure Blob Storage Data Object Read Operation Properties. When you run the mapping, the Data Integration Service reads each record and stores the respective file name in the FileName port.