this is the error generated when we use SDK and try to fetch the ptclassname. For most of the tags its not a problem but for some few it fails
What version of the PI SDK and PI Data Archive? Does it constantly happen for the same points? Can you pick one for which this error is constantly thrown and share it's configuration with us?
This error is thrown from your custom PI SDK application correct? Can you have a look on the SDK logs on the PI Data Archive to see if there are any messages around the time this error was thrown?
Retrieving data ...