Reading/writing OPC DA Tags delay

[golubyatniks]

Hello everyone,

We're using WinCC OA 3.14 patch 20, testing Getting Started project.
WinCC OA OPC DA Server manager is added, OPCRead and OPCWrite access rights are set.
We're trying to read and write OPC tags data via Matricon OPC Client and some other clients. Everything works on one machine.

We measured average reading and writing time for one tag. For WINCC_OA.OPC.1 average reading time is about 20 ms, same as avg writing time.
We compared this time with Matricon OPC Simulator Server, and it's time is about 100 times lesser (~0.2 ms).

So the result is that we can update (or read) only ~500 tags in a second for WinCC Server, and about 50000 tags for Matricon.
The question is why there is so big difference? Is there any approaches to make WinCC OA OPC DA Server work faster?

[alug]

Hallo,

is it not possible for you to register items in OPC Groups and use unsolicited transfer using data callback interface?
This would be far mor efficient than periodic reading.

best regards

Andreas

[golubyatniks]

Hallo, Anreas,

Thanks for advice, we will try to use callback for reading tags.
But writing tags values to server is even more important case for us. Do you have any ideas how to make WinCC OA OPC DA Server process tag writing requests faster?

[alug]

Hallo,

if you write an item to WinCC OPC Server there is some latency delay (20ms in our case) because the value have to be written
to another process. I assume the Matrikon server holds the item value in memory.
But that does not mean that you have n*latency if you write n values.

If the client writes 100items in one OPC write service the time should also be not much longer than 20ms.
So if you do synchronous write from the client, put many items in one service, than you get a high throughput

best regards

Andreas