How to get the information if a backup is running?
The information if a backup is running is stored at the datapoint element _DataManager(_2).Backup.Status.
The DPE is set by the server which is doing the backup
When the backup is started the value 1 is written.
If the backup was completed successfully the value 0 is written.
A negative value is written if an error occured during the execution of the backup.
The error codes and their description can be found in the WinCC OA documentation: System Management --> Database --> Online Backup --> Details to online backup --> Configuration of the backup