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MySQL 5.6 Reference Manual :: 14 Storage Engines :: 14.2 The InnoDB Storage Engine :: 14.2.3 Administering InnoDB :: 14.2.3.2 Adding, Removing, or Resizing InnoDB Data and Log Files
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14.2.3.2. Adding, Removing, or Resizing InnoDB Data and Log Files

This section describes what you can do when your InnoDB system tablespace runs out of room or when you want to change the size of the redo log files.

The easiest way to increase the size of the InnoDB system tablespace is to configure it from the beginning to be auto-extending. Specify the autoextend attribute for the last data file in the tablespace definition. Then InnoDB increases the size of that file automatically in 8MB increments when it runs out of space. The increment size can be changed by setting the value of the innodb_autoextend_increment system variable, which is measured in megabytes.

You can expand the system tablespace by a defined amount by adding another data file:

  • Shut down the MySQL server.

  • If the previous last data file is defined with the keyword autoextend, change its definition to use a fixed size, based on how large it has actually grown. Check the size of the data file, round it down to the closest multiple of 1024 × 1024 bytes (= 1MB), and specify this rounded size explicitly in innodb_data_file_path.

  • Add a new data file to the end of innodb_data_file_path, optionally making that file auto-extending. Only the last data file in the innodb_data_file_path can be specified as auto-extending.

  • Start the MySQL server again.

For example, this tablespace has just one auto-extending data file ibdata1: 

innodb_data_home_dir =
innodb_data_file_path = /ibdata/ibdata1:10M:autoextend

Suppose that this data file, over time, has grown to 988MB. Here is the configuration line after modifying the original data file to use a fixed size and adding a new auto-extending data file: 

innodb_data_home_dir =
innodb_data_file_path = /ibdata/ibdata1:988M;/disk2/ibdata2:50M:autoextend

When you add a new data file to the system tablespace configuration, make sure that the filename does not refer to an existing file. InnoDB creates and initializes the file when you restart the server.

Currently, you cannot remove a data file from the system tablespace. To decrease the system tablespace size, use this procedure:

  1. Use mysqldump to dump all your InnoDB tables.

  2. Stop the server.

  3. Remove all the existing tablespace files, including the ibdata and ib_log files. If you want to keep a backup copy of the information, then copy all the ib* files to another location before the removing the files in your MySQL installation.

  4. Remove any .frm files for InnoDB tables.

  5. Configure a new tablespace.

  6. Restart the server.

  7. Import the dump files.

If you want to change the number or the size of your InnoDB log files, use the following instructions. The procedure to use depends on the value of innodb_fast_shutdown, which determines whether or not to bring the system tablespace fully up-to-date before a shutdown operation:

  • If innodb_fast_shutdown is not set to 2: Stop the MySQL server and make sure that it shuts down without errors, to ensure that there is no information for outstanding transactions in the redo log. Copy the old redo log files to a safe place, in case something went wrong during the shutdown and you need them to recover the tablespace. Delete the old log files from the log file directory, edit my.cnf to change the log file configuration, and start the MySQL server again. mysqld sees that no InnoDB log files exist at startup and creates new ones.

  • If innodb_fast_shutdown is set to 2: Set innodb_fast_shutdown to 1: 

    mysql> SET GLOBAL innodb_fast_shutdown = 1;

    Then follow the instructions in the previous item.

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User Comments

Posted by Chris Wagner on June 2 2011 11:23pm[Delete] [Edit]

It is absurd that there is not a builtin function to compact the ibdata file to reclaim unused space to the OS. *ALWAYS* use innodb_file_per_table.

Posted by Przemek Malkowski on August 8 2011 11:27am[Delete] [Edit]

Shouldn't the innodb_fast_shutdown value set to 0 be the one that's advised before changing innodb logs ?
Since it does full insert buffer merge before shutting down it would be safer way to change innodb_log_file_size and/or innodb_log_files_in_group, am I wrong ?

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