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<!--
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- $PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.337 2005/07/06 14:45:12 momjian Exp $
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+ $PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.338 2005/07/14 05:13:38 tgl Exp $
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-->
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<chapter Id="runtime">
@@ -3173,7 +3173,7 @@ archive_command = 'copy "%p" /mnt/server/archivedir/"%f"' # Windows
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If on, collected statistics are zeroed out whenever the server
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is restarted. If off, statistics are accumulated across server
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restarts. The default is <literal>on</>. This option can only
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- be set at server start.
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+ be set at server start.
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</para>
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</listitem>
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</varlistentry>
@@ -3182,6 +3182,127 @@ archive_command = 'copy "%p" /mnt/server/archivedir/"%f"' # Windows
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</sect3>
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</sect2>
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+ <sect2 id="runtime-config-autovacuum">
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+ <title>Automatic Vacuuming</title>
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+
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+ <para>
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+ Beginning in <productname>PostgreSQL</> 8.1, there is an optional server
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+ process called the <firstterm>autovacuum daemon</>, whose purpose is
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+ to automate the issuance of periodic <command>VACUUM</> and
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+ <command>ANALYZE</> commands. When enabled, the autovacuum daemon
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+ runs periodically and checks for tables that have had a large number
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+ of updated or deleted tuples. This check uses the row-level statistics
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+ collection facility; therefore, the autovacuum daemon cannot be used
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+ unless <xref linkend="guc-stats-start-collector"> and
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+ <xref linkend="guc-stats-row-level"> are set TRUE. Also, it's
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+ important to allow a slot for the autovacuum process when choosing
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+ the value of <xref linkend="guc-superuser-reserved-connections">.
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+ </para>
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+
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+ <variablelist>
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+
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+ <varlistentry id="guc-autovacuum" xreflabel="autovacuum">
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+ <term><varname>autovacuum</varname> (<type>boolean</type>)</term>
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+ <indexterm>
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+ <primary><varname>autovacuum</> configuration parameter</primary>
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+ </indexterm>
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+ <listitem>
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+ <para>
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+ Controls whether the server should start the
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+ autovacuum subprocess. This is off by default.
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+ This option can only be set at server start or in the
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+ <filename>postgresql.conf</filename> file.
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+ </para>
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+ </listitem>
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+ </varlistentry>
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+
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+ <varlistentry id="guc-autovacuum-naptime" xreflabel="autovacuum_naptime">
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+ <term><varname>autovacuum_naptime</varname> (<type>integer</type>)</term>
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+ <indexterm>
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+ <primary><varname>autovacuum_naptime</> configuration parameter</primary>
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+ </indexterm>
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+ <listitem>
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+ <para>
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+ Specifies the delay between activity rounds for the autovacuum
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+ subprocess. In each round the subprocess examines one database
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+ and issues <command>VACUUM</> and <command>ANALYZE</> commands
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+ as needed for tables in that database. The delay is measured
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+ in seconds, and the default is 60.
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+ This option can only be set at server start or in the
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+ <filename>postgresql.conf</filename> file.
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+ </para>
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+ </listitem>
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+ </varlistentry>
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+
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+ <varlistentry id="guc-autovacuum-vacuum-threshold" xreflabel="autovacuum_vacuum_threshold">
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+ <term><varname>autovacuum_vacuum_threshold</varname> (<type>integer</type>)</term>
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+ <indexterm>
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+ <primary><varname>autovacuum_vacuum_threshold</> configuration parameter</primary>
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+ </indexterm>
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+ <listitem>
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+ <para>
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+ Specifies the minimum number of updated or deleted tuples needed
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+ to trigger a <command>VACUUM</> in any one table.
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+ The default is 1000.
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+ This option can only be set at server start or in the
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+ <filename>postgresql.conf</filename> file.
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+ </para>
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+ </listitem>
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+ </varlistentry>
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+
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+ <varlistentry id="guc-autovacuum-analyze-threshold" xreflabel="autovacuum_analyze_threshold">
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+ <term><varname>autovacuum_analyze_threshold</varname> (<type>integer</type>)</term>
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+ <indexterm>
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+ <primary><varname>autovacuum_analyze_threshold</> configuration parameter</primary>
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+ </indexterm>
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+ <listitem>
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+ <para>
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+ Specifies the minimum number of inserted, updated or deleted tuples
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+ needed to trigger an <command>ANALYZE</> in any one table.
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+ The default is 500.
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+ This option can only be set at server start or in the
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+ <filename>postgresql.conf</filename> file.
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+ </para>
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+ </listitem>
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+ </varlistentry>
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+
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+ <varlistentry id="guc-autovacuum-vacuum-scale-factor" xreflabel="autovacuum_vacuum_scale_factor">
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+ <term><varname>autovacuum_vacuum_scale_factor</varname> (<type>floating point</type>)</term>
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+ <indexterm>
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+ <primary><varname>autovacuum_vacuum_scale_factor</> configuration parameter</primary>
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+ </indexterm>
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+ <listitem>
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+ <para>
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+ Specifies a fraction of the table size to add to
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+ <varname>autovacuum_vacuum_threshold</varname>
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+ when deciding whether to trigger a <command>VACUUM</>.
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+ The default is 0.4.
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+ This option can only be set at server start or in the
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+ <filename>postgresql.conf</filename> file.
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+ </para>
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+ </listitem>
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+ </varlistentry>
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+
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+ <varlistentry id="guc-autovacuum-analyze-scale-factor" xreflabel="autovacuum_analyze_scale_factor">
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+ <term><varname>autovacuum_analyze_scale_factor</varname> (<type>floating point</type>)</term>
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+ <indexterm>
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+ <primary><varname>autovacuum_analyze_scale_factor</> configuration parameter</primary>
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+ </indexterm>
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+ <listitem>
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+ <para>
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+ Specifies a fraction of the table size to add to
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+ <varname>autovacuum_analyze_threshold</varname>
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+ when deciding whether to trigger an <command>ANALYZE</>.
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+ The default is 0.2.
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+ This option can only be set at server start or in the
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+ <filename>postgresql.conf</filename> file.
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+ </para>
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+ </listitem>
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+ </varlistentry>
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+
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+ </variablelist>
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+ </sect2>
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+
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<sect2 id="runtime-config-client">
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<title>Client Connection Defaults</title>
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