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55<Chapter Id="runtime">
@@ -1929,16 +1929,16 @@ archive_command = 'copy "%p" /mnt/server/archivedir/"%f"' # Win32
19291929 <term><varname>log_filename</varname> (<type>string</type>)</term>
19301930 <listitem>
19311931 <para>
1932- When <varname>redirect_stderr</> is enabled, this option
1932+ When <varname>redirect_stderr</varname > is enabled, this option
19331933 sets the file names of the created log files. The value
1934- is treated as a <systemitem>strftime</> pattern,
1935- so <literal>%</>-escapes
1934+ is treated as a <systemitem>strftime</systemitem > pattern,
1935+ so <literal>%</literal >-escapes
19361936 can be used to specify time-varying file names.
1937- If no <literal>%</>-escapes are present,
1937+ If no <literal>%</literal >-escapes are present,
19381938 <productname>PostgreSQL</productname> will
19391939 append the epoch of the new log file's open time. For example,
1940- if <varname>log_filename</> were <literal>server_log</>, then the
1941- chosen file name would be <literal>server_log.1093827753</>
1940+ if <varname>log_filename</varname > were <literal>server_log</literal >, then the
1941+ chosen file name would be <literal>server_log.1093827753</literal >
19421942 for a log starting at Sun Aug 29 19:02:33 2004 MST.
19431943 This option can only be set at server start or in the
19441944 <filename>postgresql.conf</filename> configuration file.
@@ -1950,7 +1950,7 @@ archive_command = 'copy "%p" /mnt/server/archivedir/"%f"' # Win32
19501950 <term><varname>log_rotation_age</varname> (<type>integer</type>)</term>
19511951 <listitem>
19521952 <para>
1953- When <varname>redirect_stderr</> is enabled, this option
1953+ When <varname>redirect_stderr</varname > is enabled, this option
19541954 determines the maximum lifetime of an individual log file.
19551955 After this many minutes have elapsed, a new log file will
19561956 be created. Set to zero to disable time-based creation of
@@ -1965,7 +1965,7 @@ archive_command = 'copy "%p" /mnt/server/archivedir/"%f"' # Win32
19651965 <term><varname>log_rotation_size</varname> (<type>integer</type>)</term>
19661966 <listitem>
19671967 <para>
1968- When <varname>redirect_stderr</> is enabled, this option
1968+ When <varname>redirect_stderr</varname > is enabled, this option
19691969 determines the maximum size of an individual log file.
19701970 After this many kilobytes have been emitted into a log file,
19711971 a new log file will be created. Set to zero to disable size-based
@@ -1980,19 +1980,38 @@ archive_command = 'copy "%p" /mnt/server/archivedir/"%f"' # Win32
19801980 <term><varname>log_truncate_on_rotation</varname> (<type>boolean</type>)</term>
19811981 <listitem>
19821982 <para>
1983- When <varname>redirect_stderr</> is enabled, this option will cause
1983+ When <varname>redirect_stderr</varname > is enabled, this option will cause
19841984 <productname>PostgreSQL</productname> to truncate (overwrite),
19851985 rather than append to, any existing log file of the same name.
19861986 However, truncation will occur only when a new file is being opened
19871987 due to time-based rotation, not during server startup or size-based
19881988 rotation. When false, pre-existing files will be appended to in
19891989 all cases. For example, using this option in combination with
1990- a <varname>log_filename</> like <literal>postgresql-%H.log</>
1990+ a <varname>log_filename</varname > like <literal>postgresql-%H.log</literal >
19911991 would result in generating twenty-four hourly log files and then
19921992 cyclically overwriting them.
19931993 This option can only be set at server start or in the
19941994 <filename>postgresql.conf</filename> configuration file.
19951995 </para>
1996+ <para>
1997+ Example: To keep 7 days of logs, one log file per day named
1998+ <literal>server_log.Mon</literal>, <literal>server_log.Tue</literal>,
1999+ etc, and automatically overwrite last week's log with this week's log,
2000+ set <varname>log_filename</varname> to <literal>server_log.%a</literal>,
2001+ <varname>log_truncate_on_rotation</varname> to <literal>true</literal>, and
2002+ <varname>log_rotation_age</varname> to <literal>1440</literal>.
2003+ </para>
2004+ <para>
2005+ Example: To keep 24 hours of logs, one log file per hour, but
2006+ also rotate sooner if the log file size exceeds 1GB, set
2007+ <varname>log_filename</varname> to <literal>server_log.%H%M</literal>,
2008+ <varname>log_truncate_on_rotation</varname> to <literal>true</literal>,
2009+ <varname>log_rotation_age</varname> to <literal>60</literal>, and
2010+ <varname>log_rotation_size</varname> to <literal>1000000</literal>.
2011+ Including <literal>%M</> in <varname>log_filename</varname> allows
2012+ any size-driven rotations that may occur to select a filename
2013+ different from the hour's initial filename.
2014+ </para>
19962015 </listitem>
19972016 </varlistentry>
19982017