資料存取伺服器（DA 伺服器）

Data Access servers (DA servers) provide data from different data sources (for example, process control systems) that an OPC client (for example, SAP ODA) can read. At the same time, DA servers can receive data from an OPC client and process it. Thus, OPC servers enable accessing a large number of items from a large number of data sources (for example, process control systems). Together with a DA server, the ERP system can use the following functions: Reading values from the DA server Writing values to the DA server Obtaining information about value changes in the DA server (Data Access subscription)