oc30.dll error running a vb6 application on windows 10

Question

oc30.dll error running a vb6 application on windows 10

Ball Cyrus 0

We have a legacy VB6 application that has worked flawlessly for years [20+ years]. We are now experiencing a faulting module .. oc30.dll version 3.20.0.0

I have tried a number of potential fixes including setting the security level of this dll to allow use with all applications. I have also disabled the touch screen driver as another potential fix. I have also removed all occurances of oc30.dll and reinstalled it. The application seem to shutdown after around 5 minutes.

We also have a virtual environment provided by Vmware vSphere. Strangely this seems to run perfectly fine here !

Unfortuntately we do have a number of laptop users which still require it installed locally.

I am running out of ideas on how to solve this..

Any help appeciated.

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Answer 1

Molly Lu-MSFT 2,586 Microsoft External Staff

Hello,

Thank you for posting in Microsoft Q&A.

Based on the description, I understand your question is related to oc30.dll error running a vb6 application on windows 10.

Try running the application in compatibility mode for an older version of Windows (e.g., Windows XP or Windows 7). Right-click the application executable, go to Properties > Compatibility, and select the appropriate compatibility mode.

Ensure that all Windows updates are installed on the laptops. Sometimes, missing updates can cause compatibility issues with older DLLs.

Compare the environment settings between the virtual machines and the laptops. Look for differences in installed software, drivers, or system configurations that might be affecting the DLL.

Check if there are any updates or patches available for the oc30.dll file. Sometimes, newer versions of the DLL can resolve compatibility issues.

Have a nice day.

Best Regards,

Molly

============================================

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Ball Cyrus 0 Reputation points

2025-03-21T12:01:41.0066667+00:00

Hi,

Compatibilty mode makes no difference. I cannot find a revised version of oc30.dll. I have even today, updated Oracle to 19c as I think it's related. Still no better.. If you google around this appears to be a common issue with legacy VB applications. I am none the wiser to a conclusive fix...

Best regards,

Cy
MotoX80 35,726 Reputation points

2025-03-21T13:21:35.26+00:00

Did you install this VB6 app with the setup.exe that you built with the VB6 IDE?
Ball Cyrus 0 Reputation points

2025-03-27T09:03:39.3966667+00:00

Yes, installed with the setup.exe. I've run out of ideas on how to solve this. Plenty of searching has found this is a known issue..
MotoX80 35,726 Reputation points

2025-03-27T12:17:30.2+00:00

Your problem might not be with oc30.dll itself, it might be with some OLE control that your app uses.

The application seem to shutdown after around 5 minutes.

The fact that it does launch and run for a period of time would seem to indicate that all dll's are successfully loaded.

What's it doing in those 5 minutes?

Do you have error handling and logging coded into the program? That is; do you have ON ERROR coded and test ERR.NUMBER so that it traps errors and writes to a log so that the developer can troubleshoot and fix the problem?

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oc30.dll error running a vb6 application on windows 10

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