"DisableCopySend" settings for IIS worker process in registry

Chunliang Zhang 0

Like 10 years ago, we received the following feedback from IIS support team

DisableCopySend: There is also actually a registry setting called DisableCopySend that you can set to 1 in HKLM\System\CurrentControlSet\Services\W3SVC\Performance that will prevent IIS from setting the HTTP_SEND_RESPONSE_FLAG_BUFFER_DATA.

Could anyone tell that if this setting still takes effect on Windows Server 2019/IIS10 or later? I cannot find useful information from internet.

Yurong Dai-MSFT 2,781 Reputation points Microsoft Vendor

2023-01-30T03:10:41.7633333+00:00

Hi @Chunliang Zhang，

No setting named DisableCopySend found in the registry, this setting is also not documented in the registry key documentation for IIS Worker Process (W3WP). It is difficult to reproduce your problem according to your description, please describe the details of the problem and post more information about your requirement.
Chunliang Zhang 0 Reputation points

2023-02-08T13:22:06.7+00:00

Thanks @Yurong Dai-MSFT , our client access different files hosted on IIS (Windows Server 2019/IIS10), however we observed that there are much more IIS logs with status 500 0 64 than previous (Windows Server 2012 R2/IIS 8.5). In the old OS/IIS we got much more 200 0 64 in IIS logs.

I am not sure if there are any changes in IIS may increase the 500 error. (Note that the file is received by client successfully, but still logged 500)

We have DisableCopySend set to 0 on Windows Server 2012 R2, but the setting does not take effect on Window Server 2019
Yurong Dai-MSFT 2,781 Reputation points Microsoft Vendor

2023-02-09T09:46:29.95+00:00

Hi @Chunliang Zhang，

I think the root problem you need to track down is the 500 error. There are many reasons for this error. According to the information you sent, it is impossible to determine the problem. What you should do is troubleshoot to get detailed error messages. The best way is to use Failed Request Tracing, which will provide key errors and warnings to help you locate the problem.
Lex Li (Microsoft) 4,742 Reputation points Microsoft Employee

2023-02-16T06:46:37.95+00:00

For settings that are not publicly documented, your best resource for discussion is Microsoft support team via support cases. You can open a new support case via https://support.microsoft.com and include details like under which support case number your team received the guidance on DisableCopySend so that the support team can review if anything changed internally.