iTP Secure WebServer System Administrator's Guide (Version 7.0)

Configuring the iTP Secure WebServer
iTP Secure WebServer System Administrator’s Guide—523346-012
7-19
Controlling File Caching
Controlling File Caching
To improve performance, the iTP Secure WebServer caches files it accesses. When a
file is cached, it is held open for 15 minutes, eliminating the need to open the file again
during that time. While the file is open, no maintenance can be performed on it nor can
it be moved to a different directory.
In addition to file opens, file information (retrieved by calling fstat) and actual file
content can also be cached.
The default configuration of the iTP Secure WebServer has been changed to take
advantage of the file caching enhancement. If file caching is not enabled, the iTP
Secure WebServer performs as in previous releases.
However, users might choose not to use file caching because of its increased memory
consumption. With the default configuration, up to 20MB bytes of additional memory
might be used.
A shell script, named vcache, is available in the /conf directory to validate the cache
entries in all the httpd servers. This script causes the HTTPD to verify its cached
information, ensuring current file content is provided to clients. However, the process of
validating cache entries walks through the entire cache table and might temporarily
consume system resources. Therefore, file updates should be conducted during off-
peak hours.
There are five other configuration directives you can use to handle file caching:
FileStatsCheckTime
Syntax:
FileStatsCheckTime <minutes>
Description:
Use the FileStatsCheckTime directive to specify the interval for file stats
information (information about a file retrieved via a call to fstat) refreshing. In
other words, the cached file stats are used during the period specified by
FileStatsCheckTime. If a file update is performed during this interval, the
timestamp and file contents in the response might not be up to date. Therefore,
use this directive with caution.
FileStatsCheckTime accepts a value from -1 to 600 minutes(10 hours).
Specifying a value of -1 disables checking. Specifying a value of 0 (zero) causes a
check to be performed every time the file is requested. With this setting, the
timestamp and file contents returned by the iTP Secure WebServer will always be
current.
Note: If disk files are not frequently updated, it is recommended that you use the
value of -1, and use the vcache script after files are updated.