[bcdfc53] | 1 | <?xml version="1.0" encoding="ISO-8859-1"?>
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| 2 | <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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| 3 | "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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| 4 | <!ENTITY % general-entities SYSTEM "../../general.ent">
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| 5 | %general-entities;
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| 6 | ]>
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| 7 |
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| 8 | <sect1 id="upgradedb" xreflabel="Upgrade Database">
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| 9 | <?dbhtml filename="upgradedb.html"?>
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| 10 |
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| 11 | <sect1info>
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| 12 | <date>$Date$</date>
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| 13 | </sect1info>
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| 14 |
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[fe9a4337] | 15 | <title>Important Notes About Upgrading Database Server Software</title>
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[7f6bf79b] | 16 |
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[d86ea4b] | 17 | <note><para>This section is about reinstalling database software
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| 18 | when an existing database is in use. It is not applicable for
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| 19 | initial installations or if there is no existing database for
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[7a9a7b26] | 20 | the package being updated, but users should read through it
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[b3ba4f9] | 21 | to become aware of issues that can arise in the future.</para></note>
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[d86ea4b] | 22 |
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[fe9a4337] | 23 | <para>Let's start this chapter with a dramatic screenshot of an error that
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| 24 | really happened. This error will not occur if you are installing database
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| 25 | software for the first time:</para>
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[bcdfc53] | 26 |
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| 27 | <screen>$ sudo systemctl status postgresql
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| 28 | -- postgresql.service - PostgreSQL database server
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| 29 | Loaded: loaded (/usr/lib/systemd/system/postgresql.service; enabled; vendor preset: enabled)
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| 30 | Active: failed (Result: exit-code) since Tue 2021-10-26 17:11:53 CDT; 2min 49s ago
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| 31 | Process: 17336 ExecStart=/usr/bin/pg_ctl -s -D ${PGROOT}/data start -w -t 120 (code=exited, status=1/FAILURE)
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| 32 | CPU: 7ms
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| 33 |
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| 34 | Oct 26 17:11:53 SVRNAME systemd[1]: Starting PostgreSQL database server...
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[7a9a7b26] | 35 | Oct 26 17:11:53 SRVNAME postgres[17338]: 2021-10-26 17:11:53.420 CDT [17338] FATAL:
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[d86ea4b] | 36 | database files are incompatible with server
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[7a9a7b26] | 37 | Oct 26 17:11:53 SRVNAME postgres[17338]: 2021-10-26 17:11:53.420 CDT [17338] DETAIL:
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[d86ea4b] | 38 | The data directory was initialized by PostgreSQL version 13,
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| 39 | which is not compatible with this version 14.0.
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[bcdfc53] | 40 | Oct 26 17:11:53 SRVNAME postgres[17336]: pg_ctl: could not start server
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| 41 | Oct 26 17:11:53 SRVNAME postgres[17336]: Examine the log output.
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| 42 | Oct 26 17:11:53 SRVNAME systemd[1]: postgresql.service: Control process exited, code=exited, status=1/FAILURE
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| 43 | Oct 26 17:11:53 SRVNAME systemd[1]: postgresql.service: Failed with result 'exit-code'.
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| 44 | Oct 26 17:11:53 SRVNAME systemd[1]: Failed to start PostgreSQL database server.</screen>
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| 45 |
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| 46 | <para>
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[fe9a4337] | 47 | To avoid situations like this (i.e., your database server
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| 48 | software refuses to start), read the following discussion of the best way to
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| 49 | upgrade a DBMS (Database Management System).
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[bcdfc53] | 50 | </para>
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[d86ea4b] | 51 |
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[bcdfc53] | 52 | <para>
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[fe9a4337] | 53 | The root cause of the error shown above was an upgrade
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| 54 | of the server software to a newer major version which left the
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| 55 | data files untouched. In this case, the administrator was able to recover
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| 56 | the DBMS without any loss of data.
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[7f6bf79b] | 57 | </para>
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[d86ea4b] | 58 |
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[7f6bf79b] | 59 | <para>
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[a1743b1] | 60 | Even if you are doing an initial DBMS install, read through this
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[fe9a4337] | 61 | section. It provides information about implementing backup
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| 62 | and restore procedures (or at least a strategy for creating
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| 63 | them) which will satisfy your needs and guarantee the safety
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[bcdfc53] | 64 | of your data.
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| 65 | </para>
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[8986fa9] | 66 |
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[bcdfc53] | 67 | <sect2>
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[fe9a4337] | 68 | <title>Upgrade Database Server Packages</title>
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[bcdfc53] | 69 |
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| 70 | <para>
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[d86ea4b] | 71 | Database systems work on files which hold the database metadata and the
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[fe9a4337] | 72 | data itself. The internal structure of these files is optimized for use
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| 73 | by the server software. When such server software is upgraded,
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| 74 | the new software may utilize a different file format than
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| 75 | had previously been used. Sometimes the new software can
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[a1743b1] | 76 | work with the old format as well as the new one—but without the
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[fe9a4337] | 77 | performance improvements the new format provides.
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| 78 | Other times, the new server software will
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| 79 | reformat the data files automatically after the upgrade.
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[bcdfc53] | 80 | </para>
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| 81 |
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| 82 | <para>
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[b9c353b] | 83 | Unfortunately, the most likely case is that the new server software
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[fe9a4337] | 84 | complains about out of date file formats and exits. When this happens,
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| 85 | and you have overwritten the old server software, you may end up
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| 86 | with a broken system and lost data.
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[bcdfc53] | 87 | </para>
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| 88 |
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| 89 | <para>
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[fe9a4337] | 90 | Changes in data file formats usually happen at major version changes, but
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| 91 | they can also occur at other times. Before upgrading any DBMS
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| 92 | software, check the documentation to see if this upgrade makes changes which
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[d86ea4b] | 93 | require reformatting the database.
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[bcdfc53] | 94 | </para>
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| 95 |
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| 96 | <para>
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[fe9a4337] | 97 | Of course, if you have databases with content that is not easily
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| 98 | rebuilt, it is always a good idea to create backups of the database from
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| 99 | time to time. Before upgrading the server software, you should run
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[d86ea4b] | 100 | another backup.
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[bcdfc53] | 101 | </para>
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| 102 |
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| 103 | <sect3>
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[fe9a4337] | 104 | <title>Upgrade by Backup and Restore</title>
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[bcdfc53] | 105 |
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| 106 | <note>
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| 107 | <para>
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[fe9a4337] | 108 | A backup is useless if there is no verified process
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[bcdfc53] | 109 | to restore the data from this backup. When running a
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[fe9a4337] | 110 | database server, you should not only create backups; you
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| 111 | should also verify that the restore process
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| 112 | really works. The time to test the restore procedure
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| 113 | is <emphasis>before</emphasis> you urgently need
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| 114 | to recover lost data.
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[bcdfc53] | 115 | </para>
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| 116 | </note>
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| 117 |
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| 118 | <para>
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[fe9a4337] | 119 | Most database server software provides some basic
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[d86ea4b] | 120 | tools to create backups of your data. Usually the backups created with
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| 121 | those tools can be read by newer versions of the software (via a
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[fe9a4337] | 122 | restore tool). Using older restore tools with newer backup data is
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| 123 | a bad idea; you should <emphasis>never</emphasis> blindly assume that
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[d86ea4b] | 124 | it will work. It might, but usually it doesn't.
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[bcdfc53] | 125 | </para>
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| 126 |
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| 127 | <para>
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[d86ea4b] | 128 | The easiest way to upgrade your database files is to
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[bcdfc53] | 129 | </para>
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| 130 |
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| 131 | <itemizedlist>
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[4e207bb] | 132 | <listitem>
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[bcdfc53] | 133 | <para>Create a full database backup using the old tools.</para>
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[7a9a7b26] | 134 |
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[fe9a4337] | 135 | <para>This step creates an offline copy of the database files—for
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| 136 | long term archiving, for disaster recovery, or as
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| 137 | preparation for an upgrade. This offline backup consists of either (1) a full
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| 138 | one-to-one copy of the current database files, or (2) a full backup of the
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| 139 | database files from a certain point in time, plus all the journal data (that is
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[d86ea4b] | 140 | Oracle® terminology, it is called "Continuous Archiving" or
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[fe9a4337] | 141 | "write ahead log (WAL)" in Postgresql) describing the
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| 142 | changes made after that point in time. This second form takes less time to create
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| 143 | (if the DB software provides this type of journaling) because you only have
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| 144 | to save the data that have changed since the last full backup was created.</para>
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| 145 |
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| 146 | <para>When upgrading database server software, a full backup
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[d86ea4b] | 147 | (which can be used for subsequent incremental backups) should be
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[fe9a4337] | 148 | created; but if there is a lot of data, an incremental backup will
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| 149 | suffice. The best strategy for you depends on
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[d86ea4b] | 150 | the amount of data stored in your database (is it a few hundred table
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[fe9a4337] | 151 | rows, or is it hundreds of terabytes?). A full backup in the latter case
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| 152 | can't be done quickly. To
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| 153 | fully protect your data, create a backup of the old
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| 154 | programs (and/or their sources) and save it, along with the data
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| 155 | files, to be certain there is a fallback solution if
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| 156 | the new software cannot read the old data.</para>
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[7a9a7b26] | 157 | </listitem>
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[d86ea4b] | 158 |
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[7a9a7b26] | 159 | <listitem>
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| 160 | <para>Upgrade the server software</para>
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[d86ea4b] | 161 |
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| 162 | <para>In this step, instructions to build the database server
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| 163 | software are executed just as they are shown in subsequent sections
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| 164 | talking about the DBMs like MariaDB or Postgresql. That is, build
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[7a9a7b26] | 165 | the software as usual using BLFS instructions.</para>
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| 166 | </listitem>
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[d86ea4b] | 167 |
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[7a9a7b26] | 168 | <listitem>
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| 169 | <para>Restore the database by using the new tools.</para>
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[d86ea4b] | 170 |
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| 171 | <para>To restore the data, the tools of the newly installed server
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| 172 | software should be used. During the restoration process, the new
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| 173 | tools will create and/or upgrade the data files in the format the
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[fe9a4337] | 174 | new software requires. It is assumed that newer software is capable of
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[d86ea4b] | 175 | reading old data.</para>
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[7a9a7b26] | 176 | </listitem>
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[d86ea4b] | 177 | </itemizedlist>
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[bcdfc53] | 178 |
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| 179 | <para>
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[fe9a4337] | 180 | Since you already have a backup procedure in place (and you
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[d86ea4b] | 181 | have tested your restore procedure, right?), this might
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[fe9a4337] | 182 | be the easiest way to upgrade as you can use your well known
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[5f729f8] | 183 | processes to upgrade just as you always do—at least in terms
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[bcdfc53] | 184 | of the backup and restore.
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| 185 | </para>
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| 186 |
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| 187 | </sect3>
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| 188 |
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| 189 | <sect3>
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[fe9a4337] | 190 | <title>Upgrade the Database Files by Using System Tools</title>
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[bcdfc53] | 191 |
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| 192 | <para>
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[d86ea4b] | 193 | Some database systems (for instance Postgresql) provide
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| 194 | a tool which can reformat (upgrade) the existing database
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[fe9a4337] | 195 | files to the new format.
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| 196 | If you need to restore from a backup (for example, running
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| 197 | the upgrade tool failed) you will have to reinstall the old software
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| 198 | to recover your data.
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[bcdfc53] | 199 | </para>
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| 200 |
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| 201 | <para>
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[fe9a4337] | 202 | Even though the reformatting tools might work as advertised,
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| 203 | you should create a full backup before running them. A failure
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| 204 | could cause serious damage to the database.
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[bcdfc53] | 205 | </para>
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| 206 |
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| 207 | </sect3>
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| 208 |
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| 209 | </sect2>
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| 210 |
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| 211 | <sect2>
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[fe9a4337] | 212 | <title>Notes for Specific DBMS</title>
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[8986fa9] | 213 |
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[bcdfc53] | 214 | <sect3>
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| 215 | <title>PostgreSQL</title>
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[8986fa9] | 216 |
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[bcdfc53] | 217 | <!-- might add some advanced notes for the DBMS here -->
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| 218 |
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[d86ea4b] | 219 | <para>Upstream documentation for Backup/Restore:
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[bcdfc53] | 220 | <ulink url="https://www.postgresql.org/docs/current/backup.html"/>
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| 221 | </para>
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[8986fa9] | 222 |
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[bcdfc53] | 223 | </sect3>
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| 224 |
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| 225 | <sect3>
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| 226 | <title>MariaDB</title>
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[8986fa9] | 227 |
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[bcdfc53] | 228 | <!-- might add some advanced notes for the DBMS here -->
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| 229 |
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[d86ea4b] | 230 | <para>Upstream documentation for Backup/Restore:
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[bcdfc53] | 231 | <ulink url="https://mariadb.com/kb/en/backup-and-restore-overview/"/>
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| 232 | </para>
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[8986fa9] | 233 |
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| 234 | </sect3>
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| 235 |
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| 236 | <sect3>
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| 237 | <title>Sqlite</title>
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| 238 |
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| 239 | <!-- might add some advanced notes for the DBMS here -->
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| 240 |
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[d86ea4b] | 241 | <para>Do not underestimate <application>Sqlite</application>. It is a
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[fe9a4337] | 242 | feature-rich DBMS. The main difference from the two big players above is
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[d86ea4b] | 243 | that Sqlite does not provide access via a network API. Sqlite databases
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[fe9a4337] | 244 | are always stored on the machine running the program which
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[d86ea4b] | 245 | uses the database. The manipulation of data content is done via API calls
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[8986fa9] | 246 | to library functions directly within the program.</para>
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| 247 |
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[d86ea4b] | 248 | <para>In the upstream documentation you may find the following
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| 249 | useful:</para>
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[8986fa9] | 250 |
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| 251 | <para>Documentation of the sqlite3 command line tool:
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| 252 | <ulink url="https://www.sqlite.org/cli.html"/>
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| 253 | </para>
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[d86ea4b] | 254 |
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[8986fa9] | 255 | <para>Documentation of backup API calls:
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| 256 | <ulink url="https://www.sqlite.org/backup.html"/>
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| 257 | </para>
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| 258 |
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[2c87187] | 259 | <para>Unfortunately, there is no dedicated chapter in the
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[fe9a4337] | 260 | upstream documentation talking about backup/restore, but
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[d86ea4b] | 261 | there are several articles about it on the
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[fe9a4337] | 262 | Internet. Here is an example.</para>
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[8986fa9] | 263 |
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[d86ea4b] | 264 | <para>Documentation for Backup/Restore:
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[8986fa9] | 265 | <ulink url="https://database.guide/backup-sqlite-database/"/>
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| 266 | </para>
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| 267 |
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[bcdfc53] | 268 | </sect3>
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| 269 |
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[8986fa9] | 270 | <sect3>
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| 271 | <title>Berkeley DB</title>
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| 272 |
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| 273 | <!-- might add some advanced notes for the DBMS here -->
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| 274 |
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[fe9a4337] | 275 | <para>Like <application>Sqlite</application>, this
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| 276 | software acts on local database files; there is no
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[d86ea4b] | 277 | network interface.</para>
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[8986fa9] | 278 |
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[fe9a4337] | 279 | <para>The relevant resources to back up/restore a Berkeley database
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[8986fa9] | 280 | are the man pages for <filename>db_dump</filename> and its
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| 281 | counterpart <filename>db_load</filename>.</para>
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| 282 |
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| 283 | </sect3>
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[bcdfc53] | 284 | </sect2>
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[8986fa9] | 285 |
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[bcdfc53] | 286 | </sect1>
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