An OPC client as NT service will always create its own instance of Filedpoint OPC ? Why ?

[JYC]

My Nt service applications needs to access FieldPoint via OPC. We use the stand OPC method to connect the OPC server. Here is problem we got

If the FieldPoint OPC is not running, the connectiong to the OPC will bring the FieldPoint OPC up as expected. But the FieldPoint OPC server runs as background program. But when we try to run the other NT service application to connect to the FieldPoint OPC, it will create anothe instace of the FieldPoint OPC server.

Is this right ? How can we make it work properly ?

[JohnM]

JYC,

The behavior you are seeing is not correct. You should only see one instance of the FieldPoint OPC server running at a time. I do know that there has been fixes to the FieldPoint OPC server that are available in FieldPoint Explorer 2.0.4. If you are not running this version, I highly recommend that you do, since I tested this version on a Windows NT machine with service pack 6a and did not see the problem that you are seeing. You can obtain the most recent version of FieldPoint Explorer at: http://digital.ni.com/softlib.nsf/current?OpenView&Start=1&Count=500&Expand=3#3
If upgrading FieldPoint Explorer does not fix the problem, I then recommend that you installed service pack 6a for Windows NT.

John M

[JYC]

John, Thanks for the answer.

Actually, my problem should have three questions

1. Should the Filedpoint OPC server created as background instance in this case ?

2. Does this background OPC server affect the OPC server function properly ? I don't have the hardware so I can't tell.

3. The version I run here is 204 build 137 and I do have SP6a in my system. And I also have MSDEV 6.0 with SP4 in the machine. Do you think there is someting else I have in my machine may create multiple instances problem ?

[JohnM]

JYC,

1) The FieldPoint OPC Server runs as a background instance on Windows NT and 2000 machines.

2) The background instance is the OPC Server and it should function properly.

3) Next, are you seeing FIELDP~2.EXE listed more than once in task manager? If you are, what is the name of the OPC Client software you are using to connect to the OPC server since I was unable to reproduce the problem that you are seeing.

[JYC]

We did see the *.exe listed more than once. The OPC client is developed by our company using third-party OPC kit.

[JohnM]

JYC,

Do you have access to another OPC Client that you can use to access the FieldPoint OPC Server? If you do, then I want you to launch your OPC client first, then launch the other OPC client. This test will determine if your OPC client is forcing the FieldPoint OPC server to create a second instance of itself. If you do not have access to another OPC client, then you will need to contact National Instruments Automation Support to obtain Server Explorer, an OPC client. When you contact technical support, refer them to this posting.

John M

[JYC]

John,

We solved the problem. It is Window NT DCOM/COM setup problem. We used DCOMCNFG.EXE and changed the identity from "this user" to "service account" and everything works fine now. Thanks