iTP Secure WebServer System Administrators Guide (Version 7.5+)

Common Log Format (CLF)
The common log format (CLF) is used by the access and error log files and is specified by the
AccessLog andErrorLog configuration directives (see “Configuration Directives” (page 198)). This
format is supported by other Web servers and by many log-analysis tools. If you already are using
or have such tools, you might want to use CLF.
Combined Log Format
The information logged into the access log as per the Common Log Format is devoid of the 'Referer'
and the 'User-Agent' fields. The users can specify the configuration directive CombinedLogFormat
if they want to log these two additional fields in to the access log file. For information on using this
configuration directive, see “CombinedLogFormat” (page 209).
NOTE: The CombinedLogFormat directive is available on systems running J06.04 and later
J-series RVUs and H06.15 and later H-series RVUs.
Extended Log Format (ELF)
The extended log format (ELF) is used by the extended log file and is specified by the ExtendedLog
configuration directive (see “ExtendedLog” (page 211)). ELF implements several features not available
with CLF including:
• All error and access information for a particular request is recorded in a single log entry. This
integration of information eliminates the need to correlate entries in the error log with separate
entries in the access log.
• Fields are provided for the Web-browser software type, the referrer, and the request begin
and end times.
• Fields are provided for security information, such as the name of an authenticated user.
• The name/value pairs used for the information fields support the addition of new logging
fields (such as a field for security information).
• The overall format makes it easy to write new log-analysis programs.
If you plan to write your ownlog-analysis programs, or if you must use the additional information
fields, you might want to specify ELF. CLF and ELF are described in detail in “Server Log File
Formats” (page 261).
Planning Space for Logs
Because the serverlog files can grow quickly in size, you should plan adequate space for them.
Table 10 (page 109) compares the expected daily growth in the size of the server log files for
various aggregate numbers of daily requests. This table assumes a typical entry size of 100 bytes
for the access log file and a typical entry size of 150 bytes for the extended log file. The size of
the errorlog file will depend on the frequency of access errors. Table 10 (page 109) assumes that
the error log file will grow at 20 percent the rate of the access log file.
Table 10 Required Log-File Space
Extended Log SizeError Log SizeAccess Log SizeRequests/Day
732K98K488K5,000
1.5 Mb195K976K10,000
3.0 Mb0.4 Mb1.9 Mb20,000
7.2 Mb1.0 Mb4.8 Mb50,000
14.5 Mb1.9 Mb9.7 Mb100,000
28.5 Mb3.8 Mb19.0 Mb200,000
Managing Log Files 109