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How can we track down excessive ASP queuing on IIS?

We are a large real estate company running a Web application. This application is run through Citrix (because of other apps we need to deploy). We have 11 Citrix metaframe servers, four IIS servers and one SQL server. We have been experiencing excessive ASP queuing, which then causes us to "poke" or unload the application so that the server doesn't lock up. Event Viewer is not really tracking any error messages that we see that can clue us into the problem. The software vendor says they don't experience our queuing issues for clients for which they are the ASP provider. What can we do to track down the problem? Is there anything like SQL Profiler that can track issues on an IIS server? We are dumbfounded.
You don't mention which version of IIS and ASP you're using. I'm going to guess it's IIS 5 on Windows 2000, using ASP 3.0. If that's the case, the answer to your question, "Is there anything like SQL Profiler that can track issues on an IIS server?" is "No." ASP.NET does include something similar and exposes detailed information about requests through a virtual file called trace.axd.

Issues with ASP 3.0 queuing are actually quite difficult for the system administrator to troubleshoot -- you'll need some help from the developer, and your message states that they're not willing to help. You can use the performance tool (perfmon) to better track the ASP queuing, and it might give you a clue as to the source of the problem. Perfmon also exposes information about the connection pool to the database, which is a common problem with database-driven ASP applications. There's also a great deal of SQL information available in perfmon, and analyzing it may lead you to conclude that the problem is occurring in the database. It's entirely possible that there's contention between requests in your SQL database that are causing the ASP requests to become stopped up -- especially considering you have four Web servers pointed at the database. If the application wasn't designed for this architecture, queuing could occur because multiple ASP servers attempt to lock the same database resource.

One other possible source comes to mind, and that's hardware limitations. None of your IIS servers or your SQL server are experiencing high processor utilization, correct? That's a possible cause of the queuing, but not a common one.

Good luck. I certainly wish I could give you a more direct answer, but I hope I've at least got you going in the right direction.

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