Use of Fast Response Cache Accelerator: IBM HTTP Server
System Administration IBM HTTP Server documentation

Fast Response Cache Accelerator Restrictions

Note: The Fast Response Cache Accelerator is also known as the Cache Accelerator.


  • Pages with dynamic content (e.g. SSI, CGI, Java) are not cached.
  • Default welcome pages are not cached. GET requests ending in / cannot be served out of the cache.
  • Access-protected documents, and pages requested over SSL are not cached.
  • Cache Accelerator supports only limited multi-language content negotiation. Only a single language version is cached where a given URL maps to multiple translated versions.
  • Cache Accelerator listens on all the IP adapters of a server, on the port specified by the Port directive. The Cache Accelerator cannot be configured to listen on some IP adapters, but not others.
Applies to Windows NT

Only Valid on Windows NT:

  • Files larger than 64KB are not cached.
  • Cache Accelerator does not cache files on, or log to locally mounted remote file systems (DFS, NFS, and so on).
  • IP-based Virtual Host caching is not supported. The Cache Accelerator should be disabled for those directories. Use the "AfpaCache off" directive in any IP-based virtual host definitions.
  • Name-based virtual hosts are supported.


  • Currently IBM HTTP Server Cache Accelerator does not run as a Proxy Server.
  • Expires headers are not returned on cached responses.
  • Cache Accelerator access log is not integrated into the HTTP Server access log.
Applies to Windows NT

Only Valid on Windows NT:

  • If you enable the Cache Accelerator, set the MaxRequestPerChild directive to 0, to work around a problem that occurs when the child process is killed and restarted on a loaded Web server.
  • Only one instance of the server can be active, when running the Cache Accelerator.
  • IBM HTTP Server should not be installed on a machine that is running IBM Netfinity Web Server Accelerator.
  • There are no facilities for monitoring the Cache Accelerator (number or names of the files cached, for example) other than access logging.
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