Wonderware DAServer limitations (DASSIDirect)

Is anyone aware of any performance limitations with Wonderware's DASSIDirect IO server?

Here's the scenario:

- Client has a WW9.0 app with approximately 41000 tags. PLC is an S7-400 series.

- There is ONE IO server running SMC Console w/ DASSIDirect. (There is a redundant failover IO server as well, but only 1 is active at once).

- DASSIDirect is configured with two device groups: S7PLC (1000ms update interval) and S7PLC_Slow (2000ms update interval).

- There are 10 client View nodes that all point to the same DASSIDirect service on the main IO server. Tags are fairly evenly split between two Access Names (S7PLC and S7PLC_Slow). Currently both access names are set to 'Advise All' instead of 'Advise Only Active Items'.

- There are intermittent communication problems with this system. The communications between the IO server and the PLC occasionally time out (IOStatus=0).

I am wondering if anybody is aware of any 'hard' limitations with the DASSIDirect service.

For example, could the use of 41000 tags in 2 device groups be a problem? Could there be a performance gain if we were to split the tags across more device groups with staggered poll intervals?

How about on the Wonderware side? Would there be any performance gain if we split tags across more access names (still ultimately pointing back to the same DASSIDirect service?).

How about pointing 10 clients at the single IO server - what does it take to stress DASSIDirect?

It's fairly straight-forward to test out any or all of these changes, but I'd like to make sure we're not running up against some fundamental issue here to start with.


Thanks,
Trevor

What release of DA SIDirect are you using?

it's version 1.0.101

Trevor,

We have experienced similar problems (intermittent comms failures) using SIDirect with applications of only around 6..7k tags and were advised by WW in the first instance to upgrade SIDirect to version 1.5
(Download here)

....I don't know if it will make any differnce as I haven't got around to doing it yet.


Kevin H

Trevor,

Do you need to have your access names on "Advise All"? That really puts a strain on not only the DA server, but your PLC and HMI as well. I have no experience with S7 PLC's, but I can speculate that you are really taxing the comms. Unless you absolutely need to continuously update all 41,000 tags, set the access names to "Advise only active items". Don't forget, in WW, tags in any active scripts are active items, which includes condition and data change scripts, so if you were concerned about that, it shouldn't be an issue.

Good Luck,
Jeff

Lesson I've learned is not to use any product from Wonderware that is equal or less than v2.0. Actually, higher revs for other products beside IO servers. Too many headaches and beta testing.

DASSIDirect performance

With your amount of s7 tags, i would prefer using DASS7 with a Simatic CP1613 card and a S7 CP using the H1/ISO protocol and using Simatic-Net software from Siemens.
So you have no overhead by TCP/IP encapsulation of the ISO packages. With the CP1613, the ISO protocol handling is done in the NIC by the Firmware.
It is not as cheap as the DASSIDirect solution, but ist is much more performant.