The terms BaseI and SMS are used in relation to VISA. Base refers to the DMS (dual message system) system, and VSMS or VISA SMS refers to the SMS system (single message system).
Recently, VISA has adopted a new division, when BaseI becomes VIP Authorization Only and VSMS-VIP Full Service. When working in VISA SMS mode, the operation is sent by the acquirer to the VISA network, then VISA sends the operation to the issuer, who authorizes or rejects the operation. Upon successful authorization, it is assumed that the transaction amount is debited from the client’s account. Thus, VISA SMS works in the same mode – online, when authorization and payment actually occur at the same time. A distinctive feature of DMS from SMS is the number of stages. DMS operations are performed in two stages. At the first stage, the operation works as in the VISA SMS mode, but with successful authorization, the amount of the operation is blocked, but not debited. At the second stage, settlements are made (see “Settlements between the acquirer and the issuer”) between the participants: the acquirer, VISA and the issuer at the end of the settlement period. The second stage is also called offline processing, when processing occurs after some time. Usually the length of the billing period is two or three financial days. As a result, the second stage leads to the debiting of funds from the cardholder’s account. The choice of SMS or DMS operation mode is influenced by the degree of reliability of the devices used by the acquirer and the preferred payment speed. For operations at ATMs, due to their small number in comparison with POS terminals, as a rule, choose the SMS mode. Online operations chargeback, representation, credit, and debit adjustment are used to conduct claims work on ATM transactions. In the case of POS terminals, when the DMS mode is most often selected, the claim work is carried out through the settlement files.
