Error handling

When the interface encounters an error, it writes a message to the log file. If an error is not PI point-specific, the interface determines whether it is still connected to the Data Archive. If the error is PI point-specific, the point is then marked by the interface as erroneous and is removed from the update list. The interface attempts to read erroneous points every ten minutes. If an attempt succeeds, the point is restored to active data collection.