XP SP 2 DCOM Issues

[OPC Support]

Hello Everyone,

I am an OPC Support Specialist employed by Matrikon in Edmonton, Alberta.

For testing purposes I have acquired a build of Windows XP with Service Pack 2 installed to try and keep ahead of possible DCOM Issues.

After taking a look at your White Paper specification entitled "Using OPC via DCOM with Microsoft Windows XP Service Pack 2", I have run into some complications.

After following your document step by step, I encountered a problem where my Start Menu was unable to have active programs dock into it. Random programs started to have completely irregular behavior.

The most disturbing was the fact that when I tried to revert the DCOM settings by going into the Component Services window, the second I tried to modify the properties of my computer the window disappeared preventing any changes.

I ended up having to have my computer rebuilt. After waiting a week to ensure there were no other problems with my machine, I tried your paper again and ran into the same problems.

This time I had already placed the DCOMCNFG.exe from Windows 2000 on my box. I opened it, and reverted back to standard DCOM settings. Upon restarting the machine after reverting, everything worked again.

To add injury to the insult, I am now receiving phone calls from clients experiencing the same symptoms.

Do you have any input or suggestions that can prevent this happening in the future?

Thank you very much!

Matrikon OPC Support.

OPC.Support@Matrikon.com
(780) 954-4011

[Randy]

Based on our offline conversation it appears that you have installed SP2 from an image provided by your IT department instead of installing the original XP and then using windows update to install SP2.

Can you please check if the problems appear if you do not use the SP2 image provided by your IT department? (i.e. let windows update install SP2 for you).

Regards,

[Randy]

Other OPC users have reported a similar problem. It seems to occur when you use DCOMCNFG. This is likely a bug in SP2 and the OPC Foundation will contact Microsoft about this issue.

For that reason, OPC users should not use DCOMCFG on XP SP2 until this issue is resolved.

I will post to this thread as more information becomes available.

Regards

[Jim Luth]

Microsoft has informed us that this issue may be related to the following:

The issue that is commonly observed is that only after the SP2 upgrade the DCOM Default launch permissions are not correct. We do not know how this occurs as no one has been able to send us data, we do know that simple deleting this value will regenerate the key on reboot.

So resolution is to run regedt32.exe and to look for the following key exactly as below; if it exists then DELETE ONLY the value not the entire OLE key.


HKLM\SOFTWARE\Microsoft\Ole\DefaultAccessPermission.


If the above Access Permissions settings have been modified you need to make sure that at least INTERACTIVE, SYSTEM, and Administrators have been explicitly granted "Access Permission". As an alternative you can export (for backup) and then delete the following registry value to restore the original default values.



HKLM\SOFTWARE\Microsoft\Ole\DefaultAccessPermission.

[aafg69]

Hi everyone, i am currently developing a custom opc client to fulfill mi internship project, while this i have ran into a weird problem while trying to configure an OPC server in a remote machine. Reding this post i realize it maybe very related. The Opc server i was installing was the TriangleMicroWorks SDG. I was tryingo to connect to the remote computers I could not see the SDG server in the available servers list, i thought it may be caused by dcom misconfiguration. (I have worked with SDG before but never on a XP with SP2 machine). Due to the fact that i have already posted this in another forum i will copy an paste the description:

[Jim Luth]

Did you try the possible fix suggested in my post above yours?

[aafg69]

hi
HKLM\SOFTWARE\Microsoft\Ole\DefaultAccessPermission is not in my registry

the ones i got are

HKLM\SOFTWARE\Microsoft\Ole\DefaultLaunchPermission
HKLM\SOFTWARE\Microsoft\Ole\EnableDCOM
HKLM\SOFTWARE\Microsoft\Ole\MachineAccessPermission
HKLM\SOFTWARE\Microsoft\Ole\MachineLaunchPermission

what do you sugest me to do?

thanks

[Jim Luth]

I suggest you create a new binary registry value "DefaultAccessPermission" and then reboot your computer.

[Harms Lenze]

Hi

I have also big problems with SPII, DCOM and OPC communication.
I have make all the step from the OPC white paper, but if the new fantastic windows firewall is active no opc communication between two computer works -> message 'DCOM error......'
Then I have make the changing in the windows registry HKLM\SOFTWARE\Microsoft\Ole\DefaultAccessPermission and delete all the values in the entry but not the entry himself. After reboot my computer no changing.
If I deactivate the firewall everything runs fine.
I thing I must make some more 'Exceptions' in the windows firewall as describe in the opc white paper ?

[Jim Luth]

Since your OPC communications works with the firewall disabled, you do not have any DCOM configuration problems. Please don't make any more DCOM changes if it is working with the firewall disabled.

In the exceptions list in the firewall, make sure you have added PORT 135, OPCEnum.exe and the OPC servers and clients (EXEs) that you are running.

At ICONICS we have set up many machines following the white paper and it has always worked.

Thanks for the fast answere

I have all these software enable in the firewall and become always these DCOM error message. Could it be a problem that on my host computer is only SPI and on the remote computer SPII ? Do you know any diagnostic software about DCOM or OPC communication to contain the eroor ?

[Jim Luth]

I assume you mean your host computer running SP1 has the OPC Server and your remote computer running SP2 has the OPC Client. If this is the case, try using a simple test client that will provide the exact error codes. ICONICS OPC Data Spy will do this. You can download it here:

http://www.iconics.com/support/free_tools.asp

Get the test client running with the firewall turned off, then turn it on and check the output window for the error codes.

[aafg69]

Hi jim, bad news. I just added the key to the registry and this got worse, now i still can not use the "open in a new windows feature", and now i can not even open the search box , what is more weird is that now my task bar i empty and when i minimize all windows they do not appear in the task bar but stacked over the bar :S (if you remember program manager from win 3.1, i seem like the groups stacked in the bottom of the progman windows) :S

Also i when i try to save an picture u paint it prompt an error saying it cannot registry "filename.bmp" beacause is still open" :S . I am realizing DCOM has mess not only Internet explorer but other programs too

i will try to post an image of the desktop as soon i find a way to do that

Thanks

Alvaro

[Randy]

Try deleting the HKLM\SOFTWARE\Microsoft\Ole\DefaultAccessPermission registry key.

It may no longer be possible to recover your system. You will likely need to re-install Windows XP from scratch.

That said, try to save a copy of the contents of the directory C:\WINDOWS\system32\config (this is your current registry) before you do the re-install. It may help others isolate the problem in the future.

Regards

[aafg69]

I restored previous retistry values and i return to the first situation (fixed taskbar problem). About the "DefaultAccessPermission" The problem is that in the first place, this key didn't show up, and when i delete its value, it does not recover nor regenerate as expected...

It is possible to export the whole OLE registry key of another win XP machine, i don't care i lose custom modification, i just want to recover original conf, should i give it a try or it's too risky

Again, Thanks everyone, i really apreciate your attention

Alvaro