Identifying Fast Response Cache Accelerator restrictions

This section discusses the caching and operational restrictions for the Fast Response Cache Accelerator, sometimes referred to as the Cache Accelerator. Links to related topics appear at the end of this section.

• Understanding caching restrictions
• Identifying operational restrictions
• Finding related information

Understanding caching restrictions

Caching does not occur on the following page types:

• Default welcome pages
• Access-protected documents, and pages requested over Secure Sockets Layer (SSL).

Caching limitations exist for the following situations:

• The Cache Accelerator cannot serve GET requests ending in "/" out of the cache.
• The Cache Accelerator supports only limited multilanguage content negotiation. Caching occurs for only a single language version, where a given URL maps to multiple translated versions.
• The Cache Accelerator listens on all the IP adapters of a server, on the port specified by the Port directive. You cannot configure the Cache Accelerator to listen on some IP adapters, but not others.
• Caching does not occur on files larger than 64KB.
• The Cache Accelerator does not cache files on, or log to locally mounted remote file systems, like the Network File System (NFS).
• The Cache Accelerator does not support IP-based virtual host caching. Disable the Cache Accelerator for these directories. Use the AfpaCache off directive in any IP-based virtual host definitions.

Identifying operational restrictions

The following operational restrictions apply:

• The IBM HTTP Server Cache Accelerator does not run as a proxy server.
• Cached responses do not return expired headers.
• The IBM HTTP Server access log does not integrate the Cache Accelerator access log.
• When you enable the Cache Accelerator, set the MaxRequestsPerChild directive to 0, to work around a problem that occurs when the child process stops and restarts on a loaded Web server.
• Only one active instance of the server can exist while running the Cache Accelerator.
• Do not install the IBM HTTP Server on a machine running the IBM Netfinity Web Server Accelerator.
• Only access logging facilities exist for monitoring the Cache Accelerator.

Support exists for name-based virtual hosts.

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