<programlisting>

psql "dbname=postgres replication=database" -c "IDENTIFY_SYSTEM;"

</programlisting>

However it is often more useful to use

<application>pg_receivexlog</application> (for physical replication) or

<application>pg_recvlogical</application> (for logical replication).

However, it is often more useful to use

<xref linkend="app-pgreceivexlog"> (for physical replication) or

<xref linkend="app-pgrecvlogical"> (for logical replication).

</para>

<para>

The commands accepted in walsender mode are:

<variablelist>

<varlistentry>

<term>IDENTIFY_SYSTEM

<term><literal>IDENTIFY_SYSTEM</literal>

<indexterm><primary>IDENTIFY_SYSTEM</primary></indexterm>

</term>

<listitem>

<variablelist>

<varlistentry>

<term>

systemid

<literal>systemid</literal> (<type>text</type>)

</term>

<listitem>

<para>

<varlistentry>

<term>

timeline

<literal>timeline</literal> (<type>int4</type>)

</term>

<listitem>

<para>

CurrentTimelineID. Also useful to check that the standby is

Currenttimeline ID. Also useful to check that the standby is

consistent with the master.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>

xlogpos

<literal>xlogpos</literal> (<type>text</type>)

</term>

<listitem>

<para>

<varlistentry>

<term>

dbname

<literal>dbname</literal> (<type>text</type>)

</term>

<listitem>

<para>

Database connected to orNULL.

Database connected to ornull.

</para>

</listitem>

</varlistentry>

</varlistentry>

<varlistentry>

<term>TIMELINE_HISTORY <replaceable class="parameter">tli</replaceable>

<term><literal>TIMELINE_HISTORY</literal> <replaceable class="parameter">tli</replaceable>

<indexterm><primary>TIMELINE_HISTORY</primary></indexterm>

</term>

<listitem>

<variablelist>

<varlistentry>

<term>

filename

<literal>filename</literal> (<type>text</type>)

</term>

<listitem>

<para>

Filenameof the timeline history file, e.g <filename>00000002.history</>.

File nameof the timeline history file, e.g., <filename>00000002.history</>.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>

content

<literal>content</literal> (<type>bytea</type>)

</term>

<listitem>

<para>

</varlistentry>

<varlistentry>

<term>CREATE_REPLICATION_SLOT <replaceable class="parameter">slot_name</> { <literal>PHYSICAL</> [ RESERVE_WAL ] | <literal>LOGICAL</> <replaceable class="parameter">output_plugin</> }

<term><literal>CREATE_REPLICATION_SLOT</literal> <replaceable class="parameter">slot_name</> { <literal>PHYSICAL</> [<literal>RESERVE_WAL</> ] | <literal>LOGICAL</> <replaceable class="parameter">output_plugin</> }

<indexterm><primary>CREATE_REPLICATION_SLOT</primary></indexterm>

</term>

<listitem>

<listitem>

<para>

Specify that this physical replication reserves <acronym>WAL</>

immediately; otherwise <acronym>WAL</> is only reserved upon

immediately. Otherwise, <acronym>WAL</> is only reserved upon

connection from a streaming replication client.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>START_REPLICATION [<literal>SLOT</literal> <replaceable class="parameter">slot_name</>] [<literal>PHYSICAL</literal>] <replaceable class="parameter">XXX/XXX</> [<literal>TIMELINE</literal> <replaceable class="parameter">tli</>]

<term><literal>START_REPLICATION</literal> [<literal>SLOT</literal> <replaceable class="parameter">slot_name</>] [<literal>PHYSICAL</literal>] <replaceable class="parameter">XXX/XXX</> [<literal>TIMELINE</literal> <replaceable class="parameter">tli</>]

<indexterm><primary>START_REPLICATION</primary></indexterm>

</term>

<listitem>

If <literal>TIMELINE</literal> option is specified,

streaming starts on timeline <replaceable class="parameter">tli</>;

otherwise, the server's current timeline is selected. The server can

reply with an error,e.g. if the requested section of WAL has already

reply with an error,for example if the requested section of WAL has already

been recycled. On success, server responds with a CopyBothResponse

message, and then starts to stream WAL to the frontend.

</para>

</para>

<para>

If the client requests a timeline that's not the latest, but is part of

If the client requests a timeline that's not the latest but is part of

the history of the server, the server will stream all the WAL on that

timeline starting from the requestedstartpoint, up to the point where

timeline starting from the requestedstart point up to the point where

the server switched to another timeline. If the client requests

streaming at exactly the end of an old timeline, the server responds

immediately with CommandComplete without entering COPY mode.

the server will end streaming by exiting the COPY mode. When the client

acknowledges this by also exiting COPY mode, the server sends a result

set with one row and two columns, indicating the next timeline in this

server's history. The first column is the next timeline's ID, and the

second column is theXLOG position where the switch happened. Usually,

server's history. The first column is the next timeline's ID (type <type>int8</type>), and the

second column is theWAL position where the switch happened (type <type>text</type>). Usually,

the switch position is the end of the WAL that was streamed, but there

are corner cases where the server can send some WAL from the old

timeline that it has not itself replayed before promoting. Finally, the

</listitem>

</varlistentry>

<varlistentry>

<term>START_REPLICATION <literal>SLOT</literal> <replaceable class="parameter">slot_name</> <literal>LOGICAL</literal> <replaceable class="parameter">XXX/XXX</> [ ( <replaceable>option_name</replaceable> [<replaceable>option_value</replaceable>] [, ...] ) ]</term>

<term><literal>START_REPLICATION</literal> <literal>SLOT</literal> <replaceable class="parameter">slot_name</> <literal>LOGICAL</literal> <replaceable class="parameter">XXX/XXX</> [ ( <replaceable>option_name</replaceable> [<replaceable>option_value</replaceable>] [, ...] ) ]</term>

<listitem>

<para>

Instructs server to start streaming WAL for logical replication, starting

at WAL position <replaceable class="parameter">XXX/XXX</>. The server can

reply with an error,e.g. if the requested section of WAL has already

reply with an error,for example if the requested section of WAL has already

been recycled. On success, server responds with a CopyBothResponse

message, and then starts to stream WAL to the frontend.

</para>

</varlistentry>

<varlistentry>

<term>DROP_REPLICATION_SLOT <replaceable class="parameter">slot_name</>

<term><literal>DROP_REPLICATION_SLOT</literal> <replaceable class="parameter">slot_name</>

<indexterm><primary>DROP_REPLICATION_SLOT</primary></indexterm>

</term>

<listitem>

</varlistentry>

<varlistentry>

<term>BASE_BACKUP [<literal>LABEL</literal> <replaceable>'label'</replaceable>] [<literal>PROGRESS</literal>] [<literal>FAST</literal>] [<literal>WAL</literal>] [<literal>NOWAIT</literal>] [<literal>MAX_RATE</literal> <replaceable>rate</replaceable>] [<literal>TABLESPACE_MAP</literal>]

<term><literal>BASE_BACKUP</literal> [<literal>LABEL</literal> <replaceable>'label'</replaceable>] [<literal>PROGRESS</literal>] [<literal>FAST</literal>] [<literal>WAL</literal>] [<literal>NOWAIT</literal>] [<literal>MAX_RATE</literal> <replaceable>rate</replaceable>] [<literal>TABLESPACE_MAP</literal>]

<indexterm><primary>BASE_BACKUP</primary></indexterm>

</term>

<listitem>

send back an approximate size in the header of each tablespace, which

can be used to calculate how far along the stream is done. This is

calculated by enumerating all the file sizes once before the transfer

is even started, andmay as such have a negative impact on the

performance - in particular itmay take longer before the first data

is even started, andmight as such have a negative impact on the

performance. In particular, itmight take longer before the first data

is streamed. Since the database files can change during the backup,

the size is only approximate andmay both grow and shrink between

the size is only approximate andmight both grow and shrink between

the time of approximation and the sending of the actual files.

</para>

</listitem>

<term><literal>NOWAIT</literal></term>

<listitem>

<para>

By default, the backup will wait until the last requiredxlog

By default, the backup will wait until the last requiredWAL

segment has been archived, or emit a warning if log archiving is

not enabled. Specifying <literal>NOWAIT</literal> disables both

the waiting and the warning, leaving the client responsible for

The fields in this row are:

<variablelist>

<varlistentry>

<term>spcoid</term>

<term><literal>spcoid</literal> (<type>oid</type>)</term>

<listitem>

<para>

Theoid of the tablespace, or<literal>NULL</> if it's the base

TheOID of the tablespace, ornull if it's the base

directory.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>spclocation</term>

<term><literal>spclocation</literal> (<type>text</type>)</term>

<listitem>

<para>

The full path of the tablespace directory, or<literal>NULL</>

The full path of the tablespace directory, ornull

if it's the base directory.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term>size</term>

<term><literal>size</literal> (<type>int8</type>)</term>

<listitem>

<para>

The approximate size of the tablespace, if progress report has

been requested; otherwise it's<literal>NULL</>.

been requested; otherwise it'snull.

</para>

</listitem>

</varlistentry>

</variablelist>

</para>

<para>

After the second regular result set, one or more CopyResponse results

will be sent, one forPGDATA and one for each additional tablespace other

will be sent, one forthe main data directory and one for each additional tablespace other

than <literal>pg_default</> and <literal>pg_global</>. The data in

the CopyResponse results will be a tar format (following the

<quote>ustar interchange format</> specified in the POSIX 1003.1-2008

</para>

</listitem>

</itemizedlist>

Owner, group and file mode are set if the underlying file system on

Owner, group, and file mode are set if the underlying file system on

the server supports it.

</para>

<para>

Once all tablespaces have been sent, a final regular result set will

be sent. This result set contains the end position of the

backup, given in XLogRecPtr format as a single column in a single row.

</para>

</listitem>

</varlistentry>

</variablelist>