The reason why application pools mysteriously disappear is related to Windows Server update framework 4.0. This issue effects multiple Windows Server platforms. While this is a rare event, it can cause havoc for IT administrators.
In the article below we will go into the reasons why application pools mysteriously disappear as well as how to correct the problems.
When an IT administrator installs the Windows Server update framework 4.0 there are no error alerts or warnings but in fact in the back end the application pools in IIS 6.0 simple do not display.
This results in all web sites that are hosted on the server to not be available. When a visitor comes to one of these web sites, they will get the error message “page cannot be found”.
This issue occurs as soon as an update is done on the framework.
To resolve this issue and bring back all the application pools in IIS 6.0 an IT administrator needs to verify that IIS 5.0 Isolation mode is not activated. To confirm this IT administrators should right click on “Web sites” and select “Properties” from the menu.
The nest step for an IT administrator to do is to choose “Service” tab, and disable the isolation mode check box.
At this point IT administrator will need to restart in IIS 6.0 on Windows Server.
Once all of this has been completed and the server comes back up, the application pools will once again be available within IIS manager.
Upon fixing this error within IIS 6.0, this issue will not occur again.
Microsoft is aware of this issue however as of this date they have not released a patch to correct the problem. To read more about this issue, read “IIS 6.0 Application Isolation Modes Overview“
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