500.19 Error When Enabling 32-bit Application Pool

by ebarcza 9/2/2011 10:49:00 AM

HTTP Error 500.19 - Internal Server Error
The requested page cannot be accessed because the related configuration data for the page is invalid. Module DynamicCompressionModule
Notification SendResponse
Handler StaticFile
Error Code 0x8007007e
Requested URL http://localhost:80/
Physical Path C:\inetpub\wwwroot
Logon Method Anonymous
Logon User Anonymous


Error Code 0x8007007e is:

ERROR_MOD_NOT_FOUND - The specified module could not be found.

This problem occurs because the ApplicationHost.config file or the Web.config file references a module that is invalid or that does not exist. To resolve this problem: In the ApplicationHost.config file or in the Web.config file, locate the module reference or the DLL reference that is invalid, and then fix the reference. To determine which module reference is incorrect, enable Failed Request Tracing, and then reproduce the problem.

For above specific error (mentioned in this example), DynamicCompressionModule module is causing the trouble. This is because of the XPress compression scheme module (suscomp.dll) which gets installed with WSUS. Since Compression schemes are defined globally and try to load in every application Pool, it will result in this error when 64bit version of suscomp.dll attempts to load in an application pool which is running in 32bit mode.

This module entry looks like:

<scheme name="xpress" doStaticCompression="false" doDynamicCompression="true"
dll="C:\Windows\system32\inetsrv\suscomp.dll" staticCompressionLevel="10"
dynamicCompressionLevel="0" />

Hence to get rid of this problem:

Ø Remove/Disable the XPress compression scheme from the configuration using the command below:

%windir%\system32\inetsrv\appcmd.exe set config -section:system.webServer/httpCompression /-[name='xpress']


Ø Add an attribute of "precondition= "64bitness" for this module entry so that it loads only in 64bit application pools

Refer this blog for more details on Preconditions in IIS7


Ø Use a 32bit version of suscomp.dll


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