Commit 5a23e7ab authored by Evan Hunt's avatar Evan Hunt
Browse files

document max-ixfr-ratio

parent e2f521e7
......@@ -1474,30 +1474,43 @@ controls {
 
<para>
The incremental zone transfer (IXFR) protocol is a way for
slave servers to transfer only changed data, instead of having to
secondary servers to transfer only changed data, instead of having to
transfer the entire zone. The IXFR protocol is specified in RFC
1995. See <xref linkend="proposed_standards"/>.
</para>
 
<para>
When acting as a master, <acronym>BIND</acronym> 9
When acting as a primary server, <acronym>BIND</acronym> 9
supports IXFR for those zones
where the necessary change history information is available. These
include master zones maintained by dynamic update and slave zones
include primary zones maintained by dynamic update and secondary zones
whose data was obtained by IXFR. For manually maintained master
zones, and for slave zones obtained by performing a full zone
zones, and for secondary zones obtained by performing a full zone
transfer (AXFR), IXFR is supported only if the option
<command>ixfr-from-differences</command> is set
to <userinput>yes</userinput>.
</para>
 
<para>
When acting as a slave, <acronym>BIND</acronym> 9 will
When acting as a secondary server, <acronym>BIND</acronym> 9 will
attempt to use IXFR unless
it is explicitly disabled. For more information about disabling
IXFR, see the description of the <command>request-ixfr</command> clause
of the <command>server</command> statement.
</para>
<para>
When a secondary server receives a zone via AXFR, it creates a
new copy of the zone database and then swaps it into place; during
the loading process, queries continue to be served from the old
database with no interference. When receiving a zone via IXFR,
however, changes are applied to the running zone, which may
degrade query performance during the transfer. If a server
receiving an IXFR request determines that the response size would
be similar in size to an AXFR response, it may wish to send AXFR
instead. The threshold at which this determination is made can
be configured using the <command>max-ixfr-ratio</command> option.
</para>
</section>
 
<section xml:id="split_dns"><info><title>Split DNS</title></info>
......@@ -4656,6 +4669,25 @@ badresp:1,adberr:0,findfail:0,valfail:0]
</listitem>
</varlistentry>
 
<varlistentry>
<term><command>max-ixfr-ratio</command></term>
<listitem>
<para>
Sets the size threshold (expressed as a percentage
of the size of the full zone) beyond which
<command>named</command> will choose to use an AXFR
response rather than IXFR when answering zone transfer
requests. See <xref linkend="incremental_zone_transfers"/>.
</para>
<para>
The minimum value is <literal>1%</literal>. The keyword
<literal>unlimited</literal> disables ratio checking and
allows IXFRs of any size. The default is
<literal>100%</literal>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><command>new-zones-directory</command></term>
<listitem>
......@@ -12424,6 +12456,17 @@ view "external" {
</listitem>
</varlistentry>
 
<varlistentry>
<term><command>max-ixfr-ratio</command></term>
<listitem>
<para>
See the description of
<command>max-ixfr-ratio</command> in
<xref linkend="options"/>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><command>max-journal-size</command></term>
<listitem>
......
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