SQL Data-recording with Redundant Servers

Hi Tony,
How about something like this? Call TaskNew() to start TaskOnAServer on both servers at startup. Each one will check if it the active server and only the active one will do the work.
Kind regards
David



INT
FUNCTION IsActiveServer()

STRING sLocalServerName
INT iResult;

iResult = 0;
sLocalServerName = ServerInfoEx ( "Server" , 0 , "IOServer" ) ;
IF(IODeviceInfo("SomeDevice" , 17) = sLocalServerName) THEN
iResult = 1;
END

RETURN iResult;
END



FUNCTION TaskOnAServer()

WHILE 1 DO // endless loop

IF (IsActiveServer() = 0) THEN
WHILE (IsActiveServer() = 0) DO // if not currently the active server
Sleep(10);
END

ELSE
WHILE (IsActiveServer() = 1) DO // if currently the active server

DoSomething(); // the thing you want only the active server to do

Sleep(1); // sleep a bit
END
END

END // while

END

Instead of using loops it is probably better to use tagsubscriptions. You can use the TagSubscribe() for that, there are various parameters you can define. In the callback function you can define the logging of data to the SQL and the confirmation to the controller. I usually also subscribe the values that have to go into the SQL database. In that way you don't have to use TagRead(), which can have a negative influence on the performance if you use it heavilly. You can start the subscription on the Alarm or Report Server. In the callback function use IF StrToInt(ServerInfoEx ("Alarm/Report" , 0)) = 1 THEN to only do the logging and confirmation once on the 'active' server component. The callback function is only triggered when the value of the subscribed tag changes.