What does this error message mean?
CCD = concurrent connected data variables.
The amount of active CCD is limited. Opening the HMI is using some of the available CCD.
Closing the HMI is releasing the CCD again.
When you repeatedly open and close the browser, the CCD can still be in use and getting into the limitation.
(There is a delay for releasing the CCD when closing the connection).
„If a client wants to subscribe to new data variables while no more CCDs are available, a message “CCD exceeded!” will appear and there will be no communication with these data variables.“
„If a client disconnects from the visu (e.g. browser gets closed), it will take some time until the browser session expires and the CCDs from this client become available once again (session timeout of the scada server: 2 min.).
How to solve a CCD exceeded?
Close alle open browser connection (HMI app) and wait for >2 min.
Now you should be able to open the HMI without error message.
Closing apps on iPads with a home button:
Closing apps on newer iPads without a home button:
How to prevent a CCD exceeded?
Don’t open the HMI in several browser simultaneously.
Don’t repeatedly open and close the HMI in short time.
Don’t repeatedly press reload the HMI in short time.