Disabling AFPA (fast cache accelerator) in IBM HTTP Server
 Technote (troubleshooting)
 
Problem(Abstract)
A useful debugging tip that occasionally resolves Web server performance problems is to disable AFPA (fast cache) in IBM HTTP Server. Because only sites that receive very high volumes (millions of hits a day) notice significant performance impact, this action does not interfere with normal operations. Note: This technote is only applicable to 32-bit Windows operating systems. AFPA does not support Windows 64-bit operating systems and therefore should never be enabled.
 
Resolving the problem
Perform the following steps to disable AFPA:
  1. Save a backup copy of the httpd.conf file located in the install_root/conf directory.

  2. For IBM HTTP Server V1.3:
    • Edit the original httpd.conf file and comment out the following three AFPA lines (insert "#" in front of each line):

      # AfpaEnable
      # AfpaCache on
      # AfpaLogFile "path/to/afpalog" V-ECLF

    • Add a Listen 80 directive in the httpd.conf file.

      The Listen 80 directive is needed because port 80 only binds the root process to the port. By default on Windows systems, IBM HTTP Server listens on the AFPA socket and not the default Windows socket. Adding the Listen 80 directive forces the Web server to listen on the default Windows socket when AFPA is disabled.


    For IBM HTTP Server V2.0 and V6.0:
    • If there is no <IfModule mod_afpa_cache.c> line in the httpd.conf file, follow the instructions for IBM HTTP Server V1.3.

    • If there is an <IfModule mod_afpa_cache.c> line in the httpd.conf file, comment out the LoadModule for AFPA. For example:

      #LoadModule ibm_afpa_module modules/mod_afpa_cache.so

    • If there is a Listen @@Port@@ directive below the <IfModule !mod_afpa_cache.c> (note the "!" symbol in this line), then replace it with the following:

      Listen 80

  3. Stop IBM HTTP Server.

  4. Delete the file that is referenced by the AfpaLogFile (referenced in step 2) file. The default naming convention of the log files is afpalog.* (for example, afpalog.5Sep2001).

  5. Start IBM HTTP Server.

  6. Verify that IBM HTTP Server is started and that no new afpalog.* file was created.
 
 
 


Document Information


Product categories: Software > Application Servers > Distributed Application & Web Servers > IBM HTTP Server > Adaptive Fast Path Architecture (AFPA)
Operating system(s): Windows
Software version: 6.0
Software edition:
Reference #: 1041298
IBM Group: Software Group
Modified date: Nov 13, 2008