Event ID 9001 — IIS Application Host SID Mapping Configuration

Event ID 9001 — IIS Application Host SID Mapping Configuration

Updated: March 24, 2009

Applies To: Windows Server 2008 R2

In Internet Information Services (IIS) 6.0, separate user accounts had to be created for application pools in order to isolate them. In IIS 7.0, mapped application pool SIDs (security identifiers) make this process easier. When a new Web site is created in IIS 7.0, the site receives a new application pool with the same name as the site. The Application Host Helper Service (AppHostSvc) dynamically creates a unique application pool SID based on the application pool name, and the name is mapped to the SID. Web site resources like files and directories can then be granted permissions by using the mapped application pool SID instead of separate user identities. This enables all application pools to run under the same default Network Service account, yet remain isolated.

Event Details

Product: Internet Information Services
ID: 9001
Source: Microsoft-Windows-IIS-APPHOSTSVC
Version: 7.5
Message: The Application Host Helper Service encountered an error while adding the mapping for the application pool name ‘%1’ to its SID. That particular SID is already mapped to another application pool name, causing a conflict. To resolve this issue, please change the name of this application pool. The data field contains the error number.

Change an IIS application pool name

To perform this procedure, you must have membership in Administrators, or you must have been delegated the appropriate authority.

To change the application pool name:

  1. Click Start, click Control Panel, and then click Administrative Tools.
  2. Right-click Internet Information Services (IIS) Manager and select Run as administrator.
  3. In the Connections pane, expand the server node and click Application Pools.
  4. On the Application Pools page, select the application pool you want to rename.
  5. In the Actions pane, under Edit Application Pool, click Rename, type the new name in the rename text box, and then press ENTER or click outside the rename text box.


If Application Host SID Mapping is not configured correctly, Web sites in the affected application pool will fail to serve pages. For this reason, you can verify the Application Host SID Mapping functionality by performing a test browse.

To perform a test browse:

  1. Choose a Web site or an application that is configured to run in the application pool that you want to verify.
  2. Open up your default browser or required client.
  3. Browse to a page in the Web site or application that you chose in step 1.
  4. The client should display the expected output page. If Application Host SID Mapping is configured correctly, the page will be displayed.

Related Management Information

IIS Application Host SID Mapping Configuration

Internet Information Services (IIS) 7.5


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