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Each InnoDB page (usually 16kb in size) contains a log sequence number, or LSN. The LSN is the system version number for the entire database. Each page’s LSN shows how recently it was changed.

By default, all InnoDB tables and indexes are stored in the system tablespace on one file. This option causes the server to create one tablespace file per table. To enable it, set it on your configuration file,


or start the server with --innodb_file_per_table.


This feature of Percona Server implements the ability to import arbitrary .ibd files exported using the Percona XtraBackup xtrabackup --export option.

See the the full documentation for more information.


The directory (relative to datadir) where the database server stores the files in a shared tablespace setup. This option does not affect the location of innodb_file_per_table. For example:

innodb_data_home_dir = ./

Specifies the names, sizes and location of shared tablespace files:


Specifies the location of the InnoDB log files:


The size in bytes of the memory buffer to cache data and indexes of InnoDB‘s tables. This aims to reduce disk access to provide better performance. By default:

Storage engine which provides ACID-compliant transactions and foreign key support, among others improvements over MyISAM. It is the default engine for MySQL as of the 5.5 series.
Previous default storage engine for MySQL for versions prior to 5.5. It doesn’t fully support transactions but in some scenarios may be faster than InnoDB. Each table is stored on disk in 3 files: .frm, .MYD, .MYI.
Percona XtraDB is an enhanced version of the InnoDB storage engine, designed to better scale on modern hardware, and including a variety of other features useful in high performance environments. It is fully backwards compatible, and so can be used as a drop-in replacement for standard InnoDB. More information here.
This file refers to the database server’s main configuration file. Most Linux distributions place it as /etc/mysql/my.cnf or /etc/my.cnf, but the location and name depends on the particular installation. Note that this is not the only way of configuring the server, some systems does not have one even and rely on the command options to start the server and its defaults values.
The directory in which the database server stores its databases. Most Linux distribution use /var/lib/mysql by default.
To support encryption and decryption of the backups, a new tool xbcrypt was introduced to Percona XtraBackup. This utility has been modeled after The xbstream binary to perform encryption and decryption outside of Percona XtraBackup.
To support simultaneous compression and streaming, a new custom streaming format called xbstream was introduced to Percona XtraBackup in addition to the TAR format.
Default prefix for tablespace files, e.g. ibdata1 is a 10MB auto-extensible file that MySQL creates for the shared tablespace by default.
For each table, the server will create a file with the .frm extension containing the table definition (for all storage engines).
On a multiple tablespace setup (innodb_file_per_table enabled), MySQL will store each newly created table on a file with a .ibd extension.
Each MyISAM table has .MYD (MYData) file which contains the data on it.
Each MyISAM table has .MYI (MYIndex) file which contains the table’s indexes.
Files with the .exp extension are created by Percona XtraBackup per each InnoDB tablespace when the xtrabackup --export option is used on prepare. These files can be used to import those tablespaces on Percona Server 5.5 or lower versions, see restoring individual tables”.
Each table using the MERGE storage engine, besides of a .frm file, will have .MRG file containing the names of the MyISAM tables associated with it.
File containing the Triggers associated to a table, e.g. :file:`mytable.TRG. With the .TRN file, they represent all the Trigger definitions.
File containing the Triggers’ Names associated to a table, e.g. :file:`mytable.TRN. With the .TRG file, they represent all the Trigger definitions.
Each table with the Archive Storage Engine has .ARM file which contains the metadata of it.
Each table with the Archive Storage Engine has .ARZ file which contains the data of it.
Each table with the CSV Storage Engine has .CSM file which contains the metadata of it.
Each table with the CSV Storage engine has .CSV file which contains the data of it (which is a standard Comma Separated Value file).
MySQL stores options of a database (like charset) in a file with a .opt extension in the database directory.
Each partitioned table has .par file which contains metadata about the partitions.
This documentation is developed in Launchpad as part of the Percona XtraBackup 2.4.
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