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Postgres FD Implementation
Commit be5f7fff authored by Bruce Momjian's avatar Bruce Momjian
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doc: move min_recovery_apply_delay into the right section 

Patch by Fujii Masao
parent 8c349ba5
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doc/src/sgml/recovery-config.sgml
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......@@ -142,56 +142,6 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"' # Windows
</listitem>
</varlistentry>
<varlistentry id="min-recovery-apply-delay" xreflabel="min_recovery_apply_delay">
<term><varname>min_recovery_apply_delay</varname> (<type>integer</type>)</term>
<indexterm>
<primary><varname>min_recovery_apply_delay</> recovery parameter</primary>
</indexterm>
<listitem>
<para>
By default, a standby server keeps restoring WAL records from the
primary as soon as possible. It may be useful to have a time-delayed
copy of the data, offering various options to correct data loss errors.
This parameter allows you to delay recovery by a fixed period of time,
specified in milliseconds if no unit is specified. For example, if
you set this parameter to <literal>5min</literal>, the standby will
replay each transaction commit only when the system time on the standby
is at least five minutes past the commit time reported by the master.
</para>
<para>
It is possible that the replication delay between servers exceeds the
value of this parameter, in which case no delay is added.
Note that the delay is calculated between the WAL timestamp as written
on master and the time on the current standby. Delays
in transfer because of networks or cascading replication configurations
may reduce the actual wait time significantly. If the system
clocks on master and standby are not synchronised, this may lead to
recovery applying records earlier than expected but is not a major issue
because the useful settings of the parameter are much larger than
typical time deviation between the servers. Be careful to allow for
different timezone settings on master and standby.
</para>
<para>
The delay occurs only on WAL records for COMMIT and Restore Points.
Other records may be replayed earlier than the specified delay, which
is not an issue for MVCC though may potentially increase the number
of recovery conflicts generated.
</para>
<para>
The delay occurs until the standby is promoted or triggered. After that
the standby will end recovery without further waiting.
</para>
<para>
This parameter is intended for use with streaming replication deployments,
however, if the parameter is specified it will be honoured in all cases.
Synchronous replication is not affected by this setting because there is
not yet any setting to request synchronous apply of transaction commits.
<varname>hot_standby_feedback</> will be delayed by use of this feature
which could lead to bloat on the master; use both together with care.
</para>
</listitem>
</varlistentry>
</variablelist>
</sect1>
......@@ -449,6 +399,56 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"' # Windows
</listitem>
</varlistentry>
<varlistentry id="min-recovery-apply-delay" xreflabel="min_recovery_apply_delay">
<term><varname>min_recovery_apply_delay</varname> (<type>integer</type>)</term>
<indexterm>
<primary><varname>min_recovery_apply_delay</> recovery parameter</primary>
</indexterm>
<listitem>
<para>
By default, a standby server keeps restoring WAL records from the
primary as soon as possible. It may be useful to have a time-delayed
copy of the data, offering various options to correct data loss errors.
This parameter allows you to delay recovery by a fixed period of time,
specified in milliseconds if no unit is specified. For example, if
you set this parameter to <literal>5min</literal>, the standby will
replay each transaction commit only when the system time on the standby
is at least five minutes past the commit time reported by the master.
</para>
<para>
It is possible that the replication delay between servers exceeds the
value of this parameter, in which case no delay is added.
Note that the delay is calculated between the WAL timestamp as written
on master and the time on the current standby. Delays
in transfer because of networks or cascading replication configurations
may reduce the actual wait time significantly. If the system
clocks on master and standby are not synchronised, this may lead to
recovery applying records earlier than expected but is not a major issue
because the useful settings of the parameter are much larger than
typical time deviation between the servers. Be careful to allow for
different timezone settings on master and standby.
</para>
<para>
The delay occurs only on WAL records for COMMIT and Restore Points.
Other records may be replayed earlier than the specified delay, which
is not an issue for MVCC though may potentially increase the number
of recovery conflicts generated.
</para>
<para>
The delay occurs until the standby is promoted or triggered. After that
the standby will end recovery without further waiting.
</para>
<para>
This parameter is intended for use with streaming replication deployments,
however, if the parameter is specified it will be honoured in all cases.
Synchronous replication is not affected by this setting because there is
not yet any setting to request synchronous apply of transaction commits.
<varname>hot_standby_feedback</> will be delayed by use of this feature
which could lead to bloat on the master; use both together with care.
</para>
</listitem>
</varlistentry>
</variablelist>
</sect1>
......
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