Increase the size of appRequestQueueLimit in the .NET framework
Each virtual directory on your Web server has a queue that stores requests to be passed from IIS to the .NET Framework (ASP.NET). If an application's queue becomes full, users see the HTTP 503, Server is busy, message and the queue starts to rejects requests. If your site uses telephone interviewing, you should consider increasing the queue size to prevent the Phone activity flooding its queue with requests. This change is strongly recommended, especially if you have many interviewers working at the same time.
1 On each computer running the Web Service, go to one of the following folders:
For x86 ASP.NET versions
C:\Windows\Microsoft.Net\Framework\<version>\CONFIG
For x64-bit ASP.NET versions
C:\Windows\Microsoft.Net\Framework64\<version>\CONFIG
2 Open the machine.config file.
The machine.config file location depends on the ASP.NET version. For example:
ASP.NET 1.x
%WINDIR%\Microsoft.NET\Framework\v1.1.4322
ASP.NET 2.0 / 3.5 x86
%WINDIR%\Microsoft.NET\Framework\v2.0.50727
ASP.NET 2.0 / 3.5 x64
%WINDIR%\Microsoft.NET\Framework64\v2.0.50727
ASP.NET 4.0 x86:
%WINDIR%\Microsoft.NET\Framework\v4.0.30319
ASP.NET 4.0 x64:
%WINDIR%\Microsoft.NET\Framework64\v4.0.30319
3 Find the line that starts <httpRuntime ...> (it is near the beginning of the file), and then change the value of the appRequestQueueLimit attribute to a value between 1000 and 5000 (the default setting is 5000).
If the <httpRuntime ...> section does not exist, you must manually create the section with at least the following settings (the values represent the default settings):
<httpRuntime
minFreeThreads="8"
minLocalRequestFreeThreads="4"
appRequestQueueLimit="5000"
/>
4 In the <system.web> section, add the following settings or edit your existing settings so that they contain the designated properties and values.
<system.web>
<httpRuntime minFreeThreads="88" minLocalRequestFreeThreads="76" appRequestQueueLimit="5000"/>
<processModel autoConfig="false" maxWorkerThreads="200" maxIoThreads="200"/>
<httpHandlers/>
...
</system.web>
5 Save the file, and then close it.
For more information about this change, see pages 818 and 819 of the following document:
See also