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** Troubleshooting ** "ISAPI ... aspnet_isapi.dll ...'Deadlock detected'" errors when using Controller



Users are experiencing slow performance / system crashing. The I.T. administrator opens the 'Application Log' inside Windows 'Event Viewer' on the Controller application server. There are entries similar to the one below.


Event Type: Warning
Event Source: W3SVC-WP Event Category: None
Event ID: 2262
Description: ISAPI 'C:\Windows\Microsoft.NET\Framework\v2.0.50727\aspnet_isapi.dll' reported itself as unhealthy for the following reason: 'Deadlock detected'.


There are several potential causes for these entries:

  • Scenario #1 - Incorrect settings for the performance property 'Limit the kernel request queue (number of requests)' for the Application Pool (for example 'DefaultAppPool') in Internet Information Services (IIS) Manager
    • See separate IBM Technote #1371195 for more details.
  • Scenario #2 - Overloaded server hardware
    • See separate IBM Technote #1371195 for more details.
  • Scenario #3 - Third-party bug in Microsoft's IIS webserver subsystem
    • See third-party (non-IBM) website links below for more details.


Scenario #3
Controller application server hosted on Windows 2003 server.

Resolving The Problem

Scenario #1 & #2
See separate IBM Technote #1371195.

Scenario #3

Install Microsoft Windows 2003 hotfix (reference KB 974165) onto Controller application server.

  • Steps:
  • 1. Contact third-party software provider (Microsoft) to ask for their software patch mentioned here:

    2. Download either 32-bit patch (393797_intl_i386_zip.exe) or 64-bit patch (393859_intl_x64_zip.exe) depending on the version of Windows 2003 server on your application server

    3. Unzip/extract the file

    4. Obtain a short period of downtime (no users on the Controller system)

    5. Logon to the Controller application server (web server) as an administrator, and install either the 32-bit hotfix ("NDP20SP2-KB974165-x86.exe") or 64-bit version ("NDP20SP2-KB974165-x64.exe") as appropriate

    6. Reboot application server.

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Document Information

Modified date:
15 June 2018