Transactional data is data related to a single business event such as a purchase requisition or a request for payment. When you create a requisition, for example, SAP creates an electronic document for that particular transaction. SAP gives the transaction a document number and adds the document to the transaction data that is already in the system. Whenever you complete a transaction in SAP, that is, when you create, change, or print a document in SAP, this document number appears at the bottom of the screen.