diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/config.sgml | 50 |
1 files changed, 26 insertions, 24 deletions
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index 391e4365c0c..86bf6ee9121 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -1,4 +1,4 @@ -<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.289 2010/07/03 20:43:57 tgl Exp $ --> +<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.290 2010/07/03 21:23:58 tgl Exp $ --> <chapter Id="runtime-config"> <title>Server Configuration</title> @@ -1914,6 +1914,31 @@ SET ENABLE_SEQSCAN TO OFF; </para> </listitem> </varlistentry> + + <varlistentry id="guc-vacuum-defer-cleanup-age" xreflabel="vacuum_defer_cleanup_age"> + <term><varname>vacuum_defer_cleanup_age</varname> (<type>integer</type>)</term> + <indexterm> + <primary><varname>vacuum_defer_cleanup_age</> configuration parameter</primary> + </indexterm> + <listitem> + <para> + Specifies the number of transactions by which <command>VACUUM</> and + <acronym>HOT</> updates will defer cleanup of dead row versions. The + default is zero transactions, meaning that dead row versions can be + removed as soon as possible, that is, as soon as they are no longer + visible to any open transaction. You may wish to set this to a + non-zero value on a primary server that is supporting hot standby + servers, as described in <xref linkend="hot-standby">. This allows + more time for queries on the standby to complete without incurring + conflicts due to early cleanup of rows. However, since the value + is measured in terms of number of write transactions occurring on the + primary server, it is difficult to predict just how much additional + grace time will be made available to standby queries. + This parameter can only be set in the <filename>postgresql.conf</> + file or on the server command line. + </para> + </listitem> + </varlistentry> </variablelist> </sect2> @@ -2004,29 +2029,6 @@ SET ENABLE_SEQSCAN TO OFF; </listitem> </varlistentry> - <varlistentry id="guc-vacuum-defer-cleanup-age" xreflabel="vacuum_defer_cleanup_age"> - <term><varname>vacuum_defer_cleanup_age</varname> (<type>integer</type>)</term> - <indexterm> - <primary><varname>vacuum_defer_cleanup_age</> configuration parameter</primary> - </indexterm> - <listitem> - <para> - Specifies the number of transactions by which <command>VACUUM</> and - <acronym>HOT</> updates will defer cleanup of dead row versions. The - default is 0 transactions, meaning that dead row versions will be - removed as soon as possible. You may wish to set this to a non-zero - value when planning or maintaining a Hot Standby connection, as - described in <xref linkend="hot-standby">. The recommended value is - <literal>0</> unless you have clear reason to increase it. The purpose - of the parameter is to allow the user to specify an approximate time - delay before cleanup occurs. However, it should be noted that there is - no direct link with any specific time delay and so the results will be - application and installation specific, as well as variable over time, - depending upon the transaction rate (of writes only). - </para> - </listitem> - </varlistentry> - </variablelist> </sect2> </sect1> |