To enable InnoDB tables in MySQL 3.23, see Section 13.2.2, “InnoDB in MySQL 3.23”.

From MySQL 4.0 on, the InnoDB storage engine is enabled by default. If you do not want to use InnoDB tables, skip-innodb option to your MySQL option file. tables, start the server with the --skip-innodb option to disable the InnoDB startup engine.

Two important disk-based resources managed by the InnoDB storage engine are its tablespace data files and its log files. If you specify no InnoDB configuration options, MySQL 4.0 and above create an auto-extending 10MB data file named ibdata1 and two 5MB log files named ib_logfile0 and ib_logfile1 in the MySQL data directory. (In MySQL 4.0.0 and 4.0.1, the data file is 64MB and not auto-extending.) In MySQL 3.23, InnoDB does not start if you provide no configuration options. To get good performance, you should explicitly provide InnoDB parameters as discussed in the following examples. Naturally, you should edit the settings to suit your hardware and requirements.

The examples shown here are representative. See Section 13.2.4, “InnoDB Startup Options and System Variables” for additional information about InnoDB-related configuration parameters.

To set up the InnoDB tablespace files, use the innodb_data_file_path option in the [mysqld] section of the my.cnf option file. On Windows, you can use my.ini instead. The value of innodb_data_file_path should be a list of one or more data file specifications. If you name more than one data file, separate them by semicolon (“;”) characters:

innodb_data_file_path=datafile_spec1[;datafile_spec2]...

For example, the following setting explicitly creates a tablespace having the same characteristics as the MySQL 4.0 default:

[mysqld]
innodb_data_file_path=ibdata1:10M:autoextend

This setting configures a single 10MB data file named ibdata1 that is auto-extending. No location for the file is given, so by default, InnoDB creates it in the MySQL data directory.

Sizes are specified using K, M, or G suffix letters to indicate units of KB, MB, or GB.

A tablespace containing a fixed-size 50MB data file named ibdata1 and a 50MB auto-extending file named ibdata2 in the data directory can be configured like this:

[mysqld]
innodb_data_file_path=ibdata1:50M;ibdata2:50M:autoextend

The full syntax for a data file specification includes the file name, its size, and several optional attributes:

file_name:file_size[:autoextend[:max:max_file_size]]

The autoextend and max attributes can be used only for the last data file in the innodb_data_file_path line. autoextend is available starting from MySQL 3.23.50 and 4.0.2.

If you specify the autoextend option for the last data file, InnoDB extends the data file if it runs out of free space in the tablespace. The increment is 8MB at a time by default. To modify the increment, change the innodb_autoextend_increment system variable.

If the disk becomes full, you might want to add another data file on another disk. For tablespace reconfiguration instructions, see Section 13.2.6, “Adding, Removing, or Resizing InnoDB Data and Log Files”.

InnoDB is not aware of the file system maximum file size, so be cautious on file systems where the maximum file size is a small value such as 2GB. To specify a maximum size for an auto-extending data file, use the max attribute following the autoextend attribute. The following configuration allows ibdata1 to grow up to a limit of 500MB:

[mysqld]
innodb_data_file_path=ibdata1:10M:autoextend:max:500M

InnoDB creates tablespace files in the MySQL data directory by default. To specify a location explicitly, use the innodb_data_home_dir option. For example, to use two files named ibdata1 and ibdata2 but create them in the /ibdata directory, configure InnoDB like this:

[mysqld]
innodb_data_home_dir = /ibdata
innodb_data_file_path=ibdata1:50M;ibdata2:50M:autoextend

InnoDB forms the directory path for each data file by textually concatenating the value of innodb_data_home_dir to the data file name, adding a path name separator (slash or backslash) between values if necessary. If the innodb_data_home_dir option is not mentioned in my.cnf at all, the default value is the “dot” directory ./, which means the MySQL data directory. (The MySQL server changes its current working directory to its data directory when it begins executing.)

If you specify innodb_data_home_dir as an empty string, you can specify absolute paths for the data files listed in the innodb_data_file_path value. The following example is equivalent to the preceding one:

[mysqld]
innodb_data_home_dir =
innodb_data_file_path=/ibdata/ibdata1:50M;/ibdata/ibdata2:50M:autoextend

A simple my.cnf example. Suppose that you have a computer with 512MB RAM and one hard disk. The following example shows possible configuration parameters in my.cnf or my.ini for InnoDB. The example assumes the use of MySQL-Max 3.23.50 or later or MySQL 4.0.2 or later because it uses the autoextend attribute. The example suits most users, both on Unix and Windows, who do not want to distribute InnoDB data files and log files onto several disks. It creates an auto-extending data file ibdata1 and two InnoDB log files ib_logfile0 and ib_logfile1 in the MySQL data directory. Also, the small archived InnoDB log file ib_arch_log_0000000000 that InnoDB creates automatically ends up in the data directory.

[mysqld]
# You can write your other MySQL server options here
# ...
# Data files must be able to hold your data and indexes.
# Make sure that you have enough free disk space.
innodb_data_file_path = ibdata1:10M:autoextend
#
# Set buffer pool size to 50-80% of your computer's memory
innodb_buffer_pool_size=256M
innodb_additional_mem_pool_size=20M
#
# Set the log file size to about 25% of the buffer pool size
innodb_log_file_size=64M
innodb_log_buffer_size=8M
#
innodb_flush_log_at_trx_commit=1

Note that data files must be less than 2GB in some file systems. The combined size of the log files must be less than 4GB. The combined size of data files must be at least 10MB.

When you create an InnoDB tablespace for the first time, it is best that you start the MySQL server from the command prompt. InnoDB then prints the information about the database creation to the screen, so you can see what is happening. For example, on Windows, if mysqld is located in C:\Program Files\MySQL\MySQL Server 4.1\bin, you can start it like this:

C:\> "C:\Program Files\MySQL\MySQL Server 4.1\bin\mysqld" --console

If you do not send server output to the screen, check the server's error log to see what InnoDB prints during the startup process.

For an example of what the information displayed by InnoDB should look like, see Section 13.2.3.3, “Creating the InnoDB Tablespace”.

You can place InnoDB options in the [mysqld] group of any option file that your server reads when it starts. The locations for option files are described in Section 4.2.3.3, “Using Option Files”.

If you installed MySQL on Windows using the installation and configuration wizards, the option file will be the my.ini file located in your MySQL installation directory. See Section 2.3.4.14, “The Location of the my.ini File”.

If your PC uses a boot loader where the C: drive is not the boot drive, your only option is to use the my.ini file in your Windows directory (typically C:\WINDOWS or C:\WINNT). You can use the SET command at the command prompt in a console window to print the value of WINDIR:

C:\> SET WINDIR
windir=C:\WINDOWS

To make sure that mysqld reads options only from a specific file, use the --defaults-file option as the first option on the command line when starting the server:

mysqld --defaults-file=your_path_to_my_cnf

An advanced my.cnf example. Suppose that you have a Linux computer with 2GB RAM and three 60GB hard disks at directory paths /, /dr2 and /dr3. The following example shows possible configuration parameters in my.cnf for InnoDB.

[mysqld]
# You can write your other MySQL server options here
# ...
innodb_data_home_dir =
#
# Data files must be able to hold your data and indexes
innodb_data_file_path = /ibdata/ibdata1:2000M;/dr2/ibdata/ibdata2:2000M:autoextend
#
# Set buffer pool size to 50-80% of your computer's memory,
# but make sure on Linux x86 total memory usage is < 2GB
innodb_buffer_pool_size=1G
innodb_additional_mem_pool_size=20M
innodb_log_group_home_dir = /dr3/iblogs
#
# innodb_log_arch_dir must be the same as innodb_log_group_home_dir
# (starting from 4.0.6, you can omit it)
innodb_log_arch_dir = /dr3/iblogs
#
# Set the log file size to about 25% of the buffer pool size
innodb_log_file_size=250M
innodb_log_buffer_size=8M
#
innodb_flush_log_at_trx_commit=1
innodb_lock_wait_timeout=50
#
# Uncomment the next line if you want to use it
#innodb_thread_concurrency=5

In some cases, database performance improves if the data is not all placed on the same physical disk. Putting log files on a different disk from data is very often beneficial for performance. The example illustrates how to do this. It places the two data files on different disks and places the log files on the third disk. InnoDB fills the tablespace beginning with the first data file. You can also use raw disk partitions (raw devices) as InnoDB data files, which may speed up I/O. See Section 13.2.3.2, “Using Raw Devices for the Shared Tablespace”.

innodb_buffer_pool_size
+ key_buffer_size
+ max_connections*(sort_buffer_size+read_buffer_size+binlog_cache_size)
+ max_connections*2MB

Tuning other mysqld server parameters. The following values are typical and suit most users:

[mysqld]
skip-external-locking
max_connections=200
read_buffer_size=1M
sort_buffer_size=1M
#
# Set key_buffer to 5 - 50% of your RAM depending on how much
# you use MyISAM tables, but keep key_buffer_size + InnoDB
# buffer pool size < 80% of your RAM
key_buffer_size=value