1==========
2 Glossary
3==========
4
5.. glossary::
6
7   UUID
8     Universally Unique IDentifier which uniquely identifies the state and the
9     sequence of changes node undergoes. 128-bit UUID is a classic DCE UUID
10     Version 1 (based on current time and MAC address). Although in theory this
11     UUID could be generated based on the real MAC-address, in the Galera it is
12     always (without exception) based on the generated pseudo-random addresses
13     ("locally administered" bit in the node address (in the UUID structure) is
14     always equal to unity).
15
16     Complete structure of the 128-bit UUID field and explanation for its
17     generation are as follows:
18
19     ===== ====  ======= =====================================================
20     From  To    Length  Content
21     ===== ====  ======= =====================================================
22      0     31    32     Bits 0-31 of Coordinated Universal Time (UTC) as a
23                         count of 100-nanosecond intervals since 00:00:00.00,
24                         15 October 1582, encoded as big-endian 32-bit number.
25     32     47    16     Bits 32-47 of UTC as a count of 100-nanosecond
26                         intervals since 00:00:00.00, 15 October 1582, encoded
27                         as big-endian 16-bit number.
28     48     59    12     Bits 48-59 of UTC as a count of 100-nanosecond
29                         intervals since 00:00:00.00, 15 October 1582, encoded
30                         as big-endian 16-bit number.
31     60     63     4     UUID version number: always equal to 1 (DCE UUID).
32     64     69     6     most-significants bits of random number, which
33                         generated from the server process PID and Coordinated
34                         Universal Time (UTC) as a count of 100-nanosecond
35                         intervals since 00:00:00.00, 15 October 1582.
36     70     71     2     UID variant: always equal to binary 10 (DCE variant).
37     72     79     8     8 least-significant bits of  random number, which
38                         generated from the server process PID and Coordinated
39                         Universal Time (UTC) as a count of 100-nanosecond
40                         intervals since 00:00:00.00, 15 October 1582.
41     80     80     1     Random bit ("unique node identifier").
42     81     81     1     Always equal to the one ("locally administered MAC
43                         address").
44     82    127    46     Random bits ("unique node identifier"): readed from
45                         the :file:`/dev/urandom` or (if :file:`/dev/urandom`
46                         is unavailable) generated based on the server process
47                         PID, current time and bits of the default "zero node
48                         identifier" (entropy data).
49     ===== ====  ======= =====================================================
50
51   LSN
52     Each InnoDB page (usually 16kb in size) contains a log sequence number, or
53     LSN. The LSN is the system version number for the entire database. Each
54     page's LSN shows how recently it was changed.
55
56   innodb_file_per_table
57     By default, all InnoDB tables and indexes are stored in the system
58     tablespace on one file. This option causes the server to create one
59     tablespace file per table. To enable it, set it on your configuration file,
60
61      .. code-block:: text
62
63         [mysqld]
64         innodb_file_per_table
65
66      or start the server with ``--innodb_file_per_table``.
67
68   innodb_expand_import
69     This feature of |Percona Server| implements the ability to import
70     arbitrary :term:`.ibd` files exported using the |Percona XtraBackup|
71     :option:`--export` option.
72
73     See the `the full documentation
74     <http://www.percona.com/doc/percona-server/5.5/management/innodb_expand_import.html>`_
75     for more information.
76
77   innodb_data_home_dir
78     The directory (relative to :term:`datadir`) where the database server
79     stores the files in a shared tablespace setup. This option does not affect
80     the location of :term:`innodb_file_per_table`. For example:
81
82      .. code-block:: text
83
84         [mysqld]
85         innodb_data_home_dir = ./
86
87   innodb_data_file_path
88     Specifies the names, sizes and location of shared tablespace files:
89
90      .. code-block:: text
91
92         [mysqld]
93         innodb_data_file_path=ibdata1:50M;ibdata2:50M:autoextend
94
95   innodb_log_group_home_dir
96     Specifies the location of the |InnoDB| log files:
97
98      .. code-block:: text
99
100         [mysqld]
101         innodb_log_group_home=/var/lib/mysql
102
103   innodb_buffer_pool_size
104     The size in bytes of the memory buffer to cache data and indexes of
105     |InnoDB|'s tables. This aims to reduce disk access to provide better
106     performance. By default:
107
108      .. code-block:: text
109
110         [mysqld]
111         innodb_buffer_pool_size=8MB
112
113   InnoDB
114      Storage engine which provides ACID-compliant transactions and foreign
115      key support, among others improvements over :term:`MyISAM`. It is the
116      default engine for |MySQL| as of the 8.0 series.
117
118   MyISAM
119     Previous default storage engine for |MySQL| for versions prior to 5.5. It
120     doesn't fully support transactions but in some scenarios may be faster
121     than :term:`InnoDB`. Each table is stored on disk in 3 files:
122     :term:`.frm`, :term:`.MYD`, :term:`.MYI`.
123
124   XtraDB
125     *Percona XtraDB* is an enhanced version of the InnoDB storage engine,
126     designed to better scale on modern hardware, and including a variety of
127     other features useful in high performance environments. It is fully
128     backwards compatible, and so can be used as a drop-in replacement for
129     standard InnoDB. More information `here
130     <https://www.percona.com/doc/percona-server/5.6/percona_xtradb.html>`_.
131
132   my.cnf
133     This file refers to the database server's main configuration file. Most
134     Linux distributions place it as :file:`/etc/mysql/my.cnf` or
135     :file:`/etc/my.cnf`, but the location and name depends on the particular
136     installation. Note that this is not the only way of configuring the
137     server, some systems does not have one even and rely on the command
138     options to start the server and its defaults values.
139
140   datadir
141    The directory in which the database server stores its databases. Most Linux
142    distribution use :file:`/var/lib/mysql` by default.
143
144   xbcrypt
145     To support encryption and decryption of the backups, a new tool xbcrypt
146     was introduced to |Percona XtraBackup|. This utility has been modeled
147     after The xbstream binary to perform encryption and decryption outside of
148     |Percona XtraBackup|.
149
150   xbstream
151     To support simultaneous compression and streaming, |Percona XtraBackup| uses the
152      xbstream format. For more information see :option:`--stream`
153
154   ibdata
155     Default prefix for tablespace files, e.g. :file:`ibdata1` is a 10MB
156     auto-extensible file that |MySQL| creates for the shared tablespace by
157     default.
158
159   .frm
160     For each table, the server will create a file with the ``.frm`` extension
161     containing the table definition (for all storage engines).
162
163   .ibd
164     On a multiple tablespace setup (:term:`innodb_file_per_table` enabled),
165     |MySQL| will store each newly created table on a file with a ``.ibd``
166     extension.
167
168   .MYD
169     Each |MyISAM| table has ``.MYD`` (MYData) file which contains the data on
170     it.
171
172   .MYI
173     Each |MyISAM| table has ``.MYI`` (MYIndex) file which contains the table's
174     indexes.
175
176   .exp
177     Files with the ``.exp`` extension are created by |Percona XtraBackup| per
178     each |InnoDB| tablespace when the :option:`--export` option is
179     used on prepare. These files can be used to import those tablespaces on
180     |Percona Server| 5.5 or lower versions, see :doc:`restoring individual
181     tables <xtrabackup_bin/restoring_individual_tables>`".
182
183   .MRG
184     Each table using the :program:`MERGE` storage engine, besides of a
185     :term:`.frm` file, will have :term:`.MRG` file containing the names of the
186     |MyISAM| tables associated with it.
187
188   .TRG
189     File containing the Triggers associated to a table, e.g.
190     `:file:`mytable.TRG`. With the :term:`.TRN` file, they represent all the
191     Trigger definitions.
192
193   .TRN
194     File containing the Triggers' Names associated to a table, e.g.
195     `:file:`mytable.TRN`. With the :term:`.TRG` file, they represent all the
196     Trigger definitions.
197
198   .ARM
199     Each table with the :program:`Archive Storage Engine` has ``.ARM`` file
200     which contains the metadata of it.
201
202   .ARZ
203     Each table with the :program:`Archive Storage Engine` has ``.ARZ`` file
204     which contains the data of it.
205
206   .CSM
207     Each table with the :program:`CSV Storage Engine` has ``.CSM`` file which
208     contains the metadata of it.
209
210   .CSV
211     Each table with the :program:`CSV Storage` engine has ``.CSV`` file which
212     contains the data of it (which is a standard Comma Separated Value file).
213
214   .opt
215     |MySQL| stores options of a database (like charset) in a file with a
216     :file:`.opt` extension in the database directory.
217
218   .par
219     Each partitioned table has .par file which contains metadata about the
220     partitions.
221