Dp Function

[maherhodali]

Hello Everyone,

I'm trying to connect data points from different "systems" in distributed architecture, but it appears that the dp function is not allowed in such cases.

How i can manage implementing this ? why this is not allowed in distributed system ? what other solution does WinCC OA have for dp functions in such cases.


Regards
Maher

[adaneau]

Hi Maher,

Yes datapoints from other systems arent allowed inside dpFct. However this is quite easy to workaround: just make a ctrl manager with a dpQueryConnectAll with REMOTE option inside sql statement to indicate which systems are connected (you can also use REMOTE ALL).

Be just careful with performances, especially VC/s as it may overload your script if fast changes occurs in all systems at same time. To mitigate this, you can introduce a blocking time.

BR
Alexandre

[leoknipp]

The blocking time in the query statement does not reduce the amount of messages within the systems for the dpQueryConnect call.
Only the manager executing the query is collecting data for the blocking time and then calls the work function only once after the blocking time with the complete amount of data collected during the blocking time.

When starting up the Event Manager the dp functions are initialized. At startup the identification for remote systems is not known and therefore the initialization of dp functions with remote DP elements would fail.
This is the limitiation why at dp functions only local dp elements can be used.

Best Regards
Leopold Knipp
Senior Support Specialist

[adaneau]

Hi Leo,

Yes using blocking time doesnt reduce the amount of messages but only the amount of callback function execution, which is still interesting to not overload system and run into a "too much pending callback" situation

BR
Alexandre