The “Online-offline data transfer” is based on the AddIn model specified in OPC 10001-7.
The transfer of information (Parameters) between offline nodes and the physical device is supported through OPC UA Methods. These Methods are built on device specific knowledge and functionality.
The transfer is usually terminated if an error occurs for any of the Parameters. No automatic retry will be conducted by the Server. However, whenever possible after a failure, the Server should bring the Device back into a functional state. The Client has to retry by calling the transfer Method again.
The transfer may involve thousands of Parameters so that it can take a long time (up to minutes), and with a result that may be too large for a single response. Therefore, the initiation of the transfer and the collection of result data are performed with separate Methods.
The Device shall have been locked by the Client prior to invoking these Methods (see 7).