Asp.net IIS6 - application pool recycle

I'm running an ASP.NET website on Windows 2003 IIS 6.0

Every 24-28 hours I'm getting the following error:

When the error occurrs all users are disconnected from the website.

Event Type: Warning
Event Source:   W3SVC
Event Category: None
Event ID:   1013
Date:       02/02/2010
Time:       19:29:38
User:       N/A

A process serving application pool 'DefaultAppPool' exceeded time limits during 
shut down. The process id was '1660'. 

For more information, see 开发者_运维百科Help and Support Center at   
   http://go.microsoft.com/fwlink/events.asp.

Any idea what does the error means?

Is this related to application pool recycle?

If so, is it a "must" to recycle the IIS app pool?

Yep this is IIS running a clean up, and recycling the app pool. you can change how this works by changing the setting on the applicationn pool..

IIS 6 Configuring Worker Processes for Recycling

This can also be caused by deadlocks on the threadpool for your application. You may need to adjust the worker threads in your machine.config or alter that recycling settings adjust how often/when the recycling occurs based on processes or virtual memory.

Contention, poor performance, and deadlocks when you make Web service requests from ASP.NET applications