levels. This parameter can only be set at server start.

</para>

<para>

In <literal>minimal</literal> level, no information is logged for

permanent relations for the remainder of a transaction that creates or

rewrites them. This can make operations much faster (see

The <literal>minimal</literal> level generates the least WAL

volume. It logs no row information for permanent relations

in transactions that create or

rewrite them. This can make operations much faster (see

<xref linkend="populate-pitr"/>). Operations that initiate this

optimization include:

<simplelist>

<member><command>REINDEX</command></member>

<member><command>TRUNCATE</command></member>

</simplelist>

But minimal WAL does not contain enough information to reconstruct the

data from a base backup and the WAL logs, so <literal>replica</literal> or

higher must be used to enable WAL archiving

(<xref linkend="guc-archive-mode"/>) and streaming replication.

However, minimal WAL does not contain sufficient information for

point-in-time recovery, so <literal>replica</literal> or

higher must be used to enable continuous archiving

(<xref linkend="guc-archive-mode"/>) and streaming binary replication.

In fact, the server will not even start in this mode if

<varname>max_wal_senders</varname> is non-zero.

Note that changing <varname>wal_level</varname> to

<literal>minimal</literal> makes any base backups taken before

unavailable for archive recovery and standby server, which may

lead to data loss.

<literal>minimal</literal> makes previous base backups unusable

for point-in-time recovery and standby servers.

</para>

<para>

In <literal>logical</literal> level, the same information is logged as

with <literal>replica</literal>, plus information needed to allow

extracting logical change sets from the WAL. Using a level of

with <literal>replica</literal>, plus information needed to

extract logical change sets from the WAL. Using a level of

<literal>logical</literal> will increase the WAL volume, particularly if many

tables are configured for <literal>REPLICA IDENTITY FULL</literal> and

many <command>UPDATE</command> and <command>DELETE</command> statements are