index 2522f4c8c57f143b7603de821c4636642f5107fd..353d4e808afc22667a9c5ceb475bc68dcd1e35d8 100644 (file)
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