# OPC UA struct data type? **URL:** \ **Category:** Ignition\ **Created:** [July 26, 2019, 1:13pm UTC](https://forum.inductiveautomation.com/t/opc-ua-struct-data-type/26905 "2019-07-26T13:13:17Z")\ **Posts on this page:** 1\ **Showing post:** 60
**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\ **Post date:** [September 28, 2023, 12:12pm UTC](https://forum.inductiveautomation.com/t/opc-ua-struct-data-type/26905/60 "2023-09-28T12:12:25Z")
Drag and drop works, you’re not doing anything wrong really, but when using this “Service Interface” mechanism in the S7-1200 we’re not able to read structures. > [@OPC connections between Ignition and Siemens PLC](https://forum.inductiveautomation.com/t/opc-connections-between-ignition-and-siemens-plc/73887/12): > > Another thing I will mention, since I missed that this was a S7-1200, is that via the “Server Interface” mechanism Ignition will not be able to read whole structures, only individual exposed structure members. I can’t remember if the 1200 exposes these or not, but it’s not ideal performance-wise for the PLC. This is because the 1200’s Service Interface mechanism only supports the newer DataTypeDefinition attribute, and not the older DataType Dictionary mechanism, that let’s clients learn about … --- _[View the full topic](https://forum.inductiveautomation.com/t/opc-ua-struct-data-type/26905)._