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><A
NAME="ARCHIVE-RECOVERY-SETTINGS"
>26.1. Archive Recovery Settings</A
></H1
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
><A
NAME="RESTORE-COMMAND"
></A
><TT
CLASS="VARNAME"
>restore_command</TT
> (<TT
CLASS="TYPE"
>string</TT
>)</DT
><DD
><P
> The shell command to execute to retrieve an archived segment of
the WAL file series. This parameter is required for archive recovery,
but optional for streaming replication.
Any <TT
CLASS="LITERAL"
>%f</TT
> in the string is
replaced by the name of the file to retrieve from the archive,
and any <TT
CLASS="LITERAL"
>%p</TT
> is replaced by the copy destination path name
on the server.
(The path name is relative to the current working directory,
i.e., the cluster's data directory.)
Any <TT
CLASS="LITERAL"
>%r</TT
> is replaced by the name of the file containing the
last valid restart point. That is the earliest file that must be kept
to allow a restore to be restartable, so this information can be used
to truncate the archive to just the minimum required to support
restarting from the current restore. <TT
CLASS="LITERAL"
>%r</TT
> is typically only
used by warm-standby configurations
(see <A
HREF="warm-standby.html"
>Section 25.2</A
>).
Write <TT
CLASS="LITERAL"
>%%</TT
> to embed an actual <TT
CLASS="LITERAL"
>%</TT
> character.
</P
><P
> It is important for the command to return a zero exit status
only if it succeeds. The command <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>will</I
></SPAN
> be asked for file
names that are not present in the archive; it must return nonzero
when so asked. Examples:
</P><PRE
CLASS="PROGRAMLISTING"
>restore_command = 'cp /mnt/server/archivedir/%f "%p"'
restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"' # Windows</PRE
><P>
</P
></DD
><DT
><A
NAME="ARCHIVE-CLEANUP-COMMAND"
></A
><TT
CLASS="VARNAME"
>archive_cleanup_command</TT
> (<TT
CLASS="TYPE"
>string</TT
>)</DT
><DD
><P
> This optional parameter specifies a shell command that will be executed
at every restartpoint. The purpose of
<TT
CLASS="VARNAME"
>archive_cleanup_command</TT
> is to provide a mechanism for
cleaning up old archived WAL files that are no longer needed by the
standby server.
Any <TT
CLASS="LITERAL"
>%r</TT
> is replaced by the name of the file containing the
last valid restart point.
That is the earliest file that must be <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>kept</I
></SPAN
> to allow a
restore to be restartable, and so all files earlier than <TT
CLASS="LITERAL"
>%r</TT
>
may be safely removed.
This information can be used to truncate the archive to just the
minimum required to support restart from the current restore.
The <A
HREF="pgarchivecleanup.html"
><SPAN
CLASS="APPLICATION"
>pg_archivecleanup</SPAN
></A
> module
is often used in <TT
CLASS="VARNAME"
>archive_cleanup_command</TT
> for
single-standby configurations, for example:
</P><PRE
CLASS="PROGRAMLISTING"
>archive_cleanup_command = 'pg_archivecleanup /mnt/server/archivedir %r'</PRE
><P>
Note however that if multiple standby servers are restoring from the
same archive directory, you will need to ensure that you do not delete
WAL files until they are no longer needed by any of the servers.
<TT
CLASS="VARNAME"
>archive_cleanup_command</TT
> would typically be used in a
warm-standby configuration (see <A
HREF="warm-standby.html"
>Section 25.2</A
>).
Write <TT
CLASS="LITERAL"
>%%</TT
> to embed an actual <TT
CLASS="LITERAL"
>%</TT
> character in the
command.
</P
><P
> If the command returns a non-zero exit status then a WARNING log
message will be written.
</P
></DD
><DT
><A
NAME="RECOVERY-END-COMMAND"
></A
><TT
CLASS="VARNAME"
>recovery_end_command</TT
> (<TT
CLASS="TYPE"
>string</TT
>)</DT
><DD
><P
> This parameter specifies a shell command that will be executed once only
at the end of recovery. This parameter is optional. The purpose of the
<TT
CLASS="VARNAME"
>recovery_end_command</TT
> is to provide a mechanism for cleanup
following replication or recovery.
Any <TT
CLASS="LITERAL"
>%r</TT
> is replaced by the name of the file containing the
last valid restart point, like in <A
HREF="archive-recovery-settings.html#ARCHIVE-CLEANUP-COMMAND"
>archive_cleanup_command</A
>.
</P
><P
> If the command returns a non-zero exit status then a WARNING log
message will be written and the database will proceed to start up
anyway. An exception is that if the command was terminated by a
signal, the database will not proceed with startup.
</P
></DD
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