ISAPI filter does not show up as "loaded" in UI

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Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1

In an effort to optimize resources in IIS 6.0, an ISAPI filter is not loaded until a request is made to a Web site that requires the ISAPI filter. Until this request is made, IIS Manager does not display the status of the ISAPI filter. Also, if the ISAPI filter requires the SF_NOTIFY_READ_RAW_DATA filter notification, the filter will not load while IIS is running in worker process isolation mode. Review the Application Event Log for events from W3SVC-WP to verify that the filter did not load. To remedy this problem, run IIS in IIS 5.0 isolation mode or contact the vendor of the ISAPI filter for compatibility updates.

Important

If the ISAPI filter is restricted by an access control list (ACL) in such a way that the IIS worker process identity cannot load it, requests receive a 503 error. To remedy this, set the ACLs on the ISAPI filter DLL to allow access for the IIS_WPG group.

Procedures

To configure IIS for IIS 5.0 isolation mode

  1. In IIS Manager, expand the local computer, right-click Web Sites, and then click Properties.

  2. Click the Service tab, select the Run WWW service in IIS 5.0 isolation mode check box, and then click OK.

  3. To start the WWW service, click Yes.