@ -2029,9 +2029,9 @@ include_dir 'conf.d'
<varname>wal_level</> determines how much information is written
to the WAL. The default value is <literal>minimal</>, which writes
only the information needed to recover from a crash or immediate
shutdown. <literal>a rchiv e</> adds logging required for WAL archiving;
<literal>hot_standby</> further add s information required to run
read-only queries on a standby server; and, finally
shutdown. <literal>replica </> adds logging required for WAL
archiving as well a s information required to run
read-only queries on a standby server. Finally,
<literal>logical</> adds information necessary to support logical
decoding. Each level includes the information logged at all lower
levels. This parameter can only be set at server start.
@ -2049,30 +2049,24 @@ include_dir 'conf.d'
transaction</member>
</simplelist>
But minimal WAL does not contain enough information to reconstruct the
data from a base backup and the WAL logs, so <literal>a rchiv e</> or
data from a base backup and the WAL logs, so <literal>replica </> or
higher must be used to enable WAL archiving
(<xref linkend="guc-archive-mode">) and streaming replication.
</para>
<para>
In <literal>hot_standby</> level, the same information is logged as
with <literal>archive</>, plus information needed to reconstruct
the status of running transactions from the WAL. To enable read-only
queries on a standby server, <varname>wal_level</> must be set to
<literal>hot_standby</> or higher on the primary, and
<xref linkend="guc-hot-standby"> must be enabled in the standby. It is
thought that there is little measurable difference in performance
between using <literal>hot_standby</> and <literal>archive</> levels,
so feedback is welcome if any production impacts are noticeable.
</para>
<para>
In <literal>logical</> level, the same information is logged as
with <literal>hot_standby </>, plus information needed to allow
with <literal>replica</>, plus information needed to allow
extracting logical change sets from the WAL. Using a level of
<literal>logical</> will increase the WAL volume, particularly if many
tables are configured for <literal>REPLICA IDENTITY FULL</literal> and
many <command>UPDATE</> and <command>DELETE</> statements are
executed.
</para>
<para>
In releases prior to 9.6, this parameter also allowed the
values <literal>archive</literal> and <literal>hot_standby</literal>.
These are still accepted but mapped to <literal>replica</literal>.
</para>
</listitem>
</varlistentry>
@ -2784,7 +2778,7 @@ include_dir 'conf.d'
higher than the maximum number of expected clients so disconnected
clients can immediately reconnect. This parameter can only
be set at server start. <varname>wal_level</> must be set to
<literal>a rchiv e</> or higher to allow connections from standby
<literal>replica </> or higher to allow connections from standby
servers.
</para>
</listitem>
@ -2803,7 +2797,7 @@ include_dir 'conf.d'
can support. The default is zero. This parameter can only be set at
server start.
<varname>wal_level</varname> must be set
to <literal>a rchiv e</literal> or higher to allow replication slots to
to <literal>replica </literal> or higher to allow replication slots to
be used. Setting it to a lower value than the number of currently
existing replication slots will prevent the server from starting.
</para>