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Commitdc21234

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Add support for incremental backup.
To take an incremental backup, you use the new replication commandUPLOAD_MANIFEST to upload the manifest for the prior backup. Thisprior backup could either be a full backup or another incrementalbackup. You then use BASE_BACKUP with the INCREMENTAL option to takethe backup. pg_basebackup now has an --incremental=PATH_TO_MANIFESToption to trigger this behavior.An incremental backup is like a regular full backup except thatsome relation files are replaced with files with names likeINCREMENTAL.${ORIGINAL_NAME}, and the backup_label file containsadditional lines identifying it as an incremental backup. The newpg_combinebackup tool can be used to reconstruct a data directoryfrom a full backup and a series of incremental backups.Patch by me. Reviewed by Matthias van de Meent, Dilip Kumar, JakubWartak, Peter Eisentraut, and Álvaro Herrera. Thanks especially toJakub for incredibly helpful and extensive testing.Discussion:http://postgr.es/m/CA+TgmoYOYZfMCyOXFyC-P+-mdrZqm5pP2N7S-r0z3_402h9rsA@mail.gmail.com
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‎doc/src/sgml/backup.sgml

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@@ -857,12 +857,79 @@ test ! -f /mnt/server/archivedir/00000001000000A900000065 && cp pg_wal/0
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</para>
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</sect2>
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<sect2 id="backup-incremental-backup">
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<title>Making an Incremental Backup</title>
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<para>
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You can use <xref linkend="app-pgbasebackup"/> to take an incremental
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backup by specifying the <literal>--incremental</literal> option. You must
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supply, as an argument to <literal>--incremental</literal>, the backup
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manifest to an earlier backup from the same server. In the resulting
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backup, non-relation files will be included in their entirety, but some
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relation files may be replaced by smaller incremental files which contain
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only the blocks which have been changed since the earlier backup and enough
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metadata to reconstruct the current version of the file.
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</para>
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<para>
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To figure out which blocks need to be backed up, the server uses WAL
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summaries, which are stored in the data directory, inside the directory
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<literal>pg_wal/summaries</literal>. If the required summary files are not
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present, an attempt to take an incremental backup will fail. The summaries
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present in this directory must cover all LSNs from the start LSN of the
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prior backup to the start LSN of the current backup. Since the server looks
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for WAL summaries just after establishing the start LSN of the current
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backup, the necessary summary files probably won't be instantly present
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on disk, but the server will wait for any missing files to show up.
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This also helps if the WAL summarization process has fallen behind.
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However, if the necessary files have already been removed, or if the WAL
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summarizer doesn't catch up quickly enough, the incremental backup will
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fail.
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</para>
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<para>
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When restoring an incremental backup, it will be necessary to have not
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only the incremental backup itself but also all earlier backups that
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are required to supply the blocks omitted from the incremental backup.
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See <xref linkend="app-pgcombinebackup"/> for further information about
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this requirement.
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</para>
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<para>
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Note that all of the requirements for making use of a full backup also
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apply to an incremental backup. For instance, you still need all of the
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WAL segment files generated during and after the file system backup, and
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any relevant WAL history files. And you still need to create a
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<literal>recovery.signal</literal> (or <literal>standby.signal</literal>)
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and perform recovery, as described in
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<xref linkend="backup-pitr-recovery" />. The requirement to have earlier
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backups available at restore time and to use
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<literal>pg_combinebackup</literal> is an additional requirement on top of
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everything else. Keep in mind that <application>PostgreSQL</application>
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has no built-in mechanism to figure out which backups are still needed as
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a basis for restoring later incremental backups. You must keep track of
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the relationships between your full and incremental backups on your own,
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and be certain not to remove earlier backups if they might be needed when
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restoring later incremental backups.
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</para>
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<para>
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Incremental backups typically only make sense for relatively large
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databases where a significant portion of the data does not change, or only
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changes slowly. For a small database, it's simpler to ignore the existence
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of incremental backups and simply take full backups, which are simpler
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to manage. For a large database all of which is heavily modified,
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incremental backups won't be much smaller than full backups.
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</para>
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</sect2>
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<sect2 id="backup-lowlevel-base-backup">
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<title>Making a Base Backup Using the Low Level API</title>
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<para>
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The procedure for making a base backup using the low level
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APIs contains a few more steps than
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the <xref linkend="app-pgbasebackup"/> method, but is relatively
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Instead of taking a full or incremental base backup using
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<xref linkend="app-pgbasebackup"/>, you can take a base backup using the
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low-level API. This procedure contains a few more steps than
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the <application>pg_basebackup</application> method, but is relatively
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simple. It is very important that these steps are executed in
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sequence, and that the success of a step is verified before
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proceeding to the next step.
@@ -1118,14 +1185,28 @@ SELECT * FROM pg_backup_stop(wait_for_archive => true);
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</listitem>
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<listitem>
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<para>
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Restore the database files from your file system backup. Be sure that they
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If you're restoring a full backup, you can restore the database files
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directly into the target directories. Be sure that they
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are restored with the right ownership (the database system user, not
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<literal>root</literal>!) and with the right permissions. If you are using
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tablespaces,
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you should verify that the symbolic links in <filename>pg_tblspc/</filename>
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were correctly restored.
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</para>
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</listitem>
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<listitem>
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<para>
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If you're restoring an incremental backup, you'll need to restore the
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incremental backup and all earlier backups upon which it directly or
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indirectly depends to the machine where you are performing the restore.
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These backups will need to be placed in separate directories, not the
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target directories where you want the running server to end up.
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Once this is done, use <xref linkend="app-pgcombinebackup"/> to pull
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data from the full backup and all of the subsequent incremental backups
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and write out a synthetic full backup to the target directories. As above,
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verify that permissions and tablespace links are correct.
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</para>
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</listitem>
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<listitem>
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<para>
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Remove any files present in <filename>pg_wal/</filename>; these came from the

‎doc/src/sgml/config.sgml

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@@ -4153,13 +4153,11 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"' # Windows
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<sect2 id="runtime-config-wal-summarization">
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<title>WAL Summarization</title>
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<!--
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<para>
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These settings control WAL summarization, a feature which must be
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enabled in order to perform an
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<link linkend="backup-incremental-backup">incremental backup</link>.
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</para>
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-->
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<variablelist>
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<varlistentry id="guc-summarize-wal" xreflabel="summarize_wal">

‎doc/src/sgml/protocol.sgml

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@@ -2599,6 +2599,19 @@ psql "dbname=postgres replication=database" -c "IDENTIFY_SYSTEM;"
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</listitem>
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</varlistentry>
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<varlistentry id="protocol-replication-upload-manifest">
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<term>
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<literal>UPLOAD_MANIFEST</literal>
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<indexterm><primary>UPLOAD_MANIFEST</primary></indexterm>
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</term>
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<listitem>
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<para>
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Uploads a backup manifest in preparation for taking an incremental
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backup.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry id="protocol-replication-base-backup" xreflabel="BASE_BACKUP">
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<term><literal>BASE_BACKUP</literal> [ ( <replaceable class="parameter">option</replaceable> [, ...] ) ]
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<indexterm><primary>BASE_BACKUP</primary></indexterm>
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>INCREMENTAL</literal></term>
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<listitem>
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<para>
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Requests an incremental backup. The
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<literal>UPLOAD_MANIFEST</literal> command must be executed
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before running a base backup with this option.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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‎doc/src/sgml/ref/allfiles.sgml

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@@ -202,6 +202,7 @@ Complete list of usable sgml source files in this directory.
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<!ENTITY pgBasebackup SYSTEM "pg_basebackup.sgml">
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<!ENTITY pgbench SYSTEM "pgbench.sgml">
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<!ENTITY pgChecksums SYSTEM "pg_checksums.sgml">
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<!ENTITY pgCombinebackup SYSTEM "pg_combinebackup.sgml">
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<!ENTITY pgConfig SYSTEM "pg_config-ref.sgml">
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<!ENTITY pgControldata SYSTEM "pg_controldata.sgml">
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<!ENTITY pgCtl SYSTEM "pg_ctl-ref.sgml">

‎doc/src/sgml/ref/pg_basebackup.sgml

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@@ -38,11 +38,25 @@ PostgreSQL documentation
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</para>
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<para>
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<application>pg_basebackup</application> makes an exact copy of the database
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cluster's files, while making sure the server is put into and
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out of backup mode automatically. Backups are always taken of the entire
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database cluster; it is not possible to back up individual databases or
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database objects. For selective backups, another tool such as
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<application>pg_basebackup</application> can take a full or incremental
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base backup of the database. When used to take a full backup, it makes an
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exact copy of the database cluster's files. When used to take an incremental
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backup, some files that would have been part of a full backup may be
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replaced with incremental versions of the same files, containing only those
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blocks that have been modified since the reference backup. An incremental
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backup cannot be used directly; instead,
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<xref linkend="app-pgcombinebackup"/> must first
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be used to combine it with the previous backups upon which it depends.
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See <xref linkend="backup-incremental-backup" /> for more information
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about incremental backups, and <xref linkend="backup-pitr-recovery" />
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for steps to recover from a backup.
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</para>
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<para>
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In any mode, <application>pg_basebackup</application> makes sure the server
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is put into and out of backup mode automatically. Backups are always taken of
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the entire database cluster; it is not possible to back up individual
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databases or database objects. For selective backups, another tool such as
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<xref linkend="app-pgdump"/> must be used.
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</para>
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@@ -197,6 +211,19 @@ PostgreSQL documentation
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>-i <replaceable class="parameter">old_manifest_file</replaceable></option></term>
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<term><option>--incremental=<replaceable class="parameter">old_meanifest_file</replaceable></option></term>
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<listitem>
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<para>
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Performs an <link linkend="backup-incremental-backup">incremental
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backup</link>. The backup manifest for the reference
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backup must be provided, and will be uploaded to the server, which will
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respond by sending the requested incremental backup.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>-R</option></term>
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<term><option>--write-recovery-conf</option></term>

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