error in read tag

[InformaticsComplex]

i am using DSC module to get data from an OPC Server. my OPC Server is running on a server and i am accessing tags on a client machine. i have used ReadTag vi in order to read tags. when i turn th opc server OFF on the server, read tag still shows data. my vi keeps on running. though i have included all error handling, but no error is shown.kindly help me in this regard.

Rubina

[CharlieM]

Rubina,

This may be expected behavior for your server and DSC but I am unsure. It is not uncommon for an OPC client to hold onto the last value it has read from the server. In such a case the quality is still good but the timestamp should be older/unchanging. You may want to look into the timestamps of your tags as well as seeing if your Server has a tag for its status that you can access with your client.

[InformaticsComplex]

well there is no tag in server that sends the server status.i  have used the Tag Status vi but that is not working as well. i have tried to use SRVR Get Status vi and SVRG Get Device Row, but they r not working. i have searched the entire site to see the use of these two vi's but could not find a proper example, can u help me in this regard that how to use these two vi's. and how can i get server's status on run time.

[Jennifer_R]

Hi Rubina,

Several of the example programs in NI Example Finder use SRVR Get Status VI.  You may be interested in Demo.vi which can be accessed from LabVIEW through Help >> Find Examples... >> Toolkits and Modules >> Datalogging and Supervisory Control >> Servers >> Demo.vi. 

Also, the "Server Shutdown" section of VI-Based Server - Developing a Server discusses the use of SRVR Read Output Queue VI in relation to the shutdown status of a server.