manual.texi:

the configuration file @file{my.cnf}, or on Windows optionally in

@file{my.ini}.

At the minimum, in 3.23 you must specify @code{innodb_data_file_path}.

At the minimum, in 3.23 you must specify @code{innodb_data_file_path}

where you specify the names and the sizes of datafiles. If you do

not mention @code{innodb_data_home_dir} in @file{my.cnf} the default

is to create these files to the @code{datadir} of MySQL.

If you specify @code{innodb_data_home_dir} as an empty string,

then you can give absolute paths to your data files in

@code{innodb_data_file_path}.

In MySQL-4.0 you do not need to specify even

@code{innodb_data_file_path}: the default for it is to create

an auto-extending 16 MB file @file{ibdata1} to the @code{datadir}

will extend the last datafile if it runs out of free space in the

tablespace. The increment is 8 MB at a time. An example:

@example

innodb_data_home_dir =

innodb_data_file_path = /ibdata/ibdata1:100M:autoextend

@end example

instructs InnoDB to create just a single datafile whose initial size is

@code{innodb_data_file_path}.

After that you can add another datafile:

@example

innodb_data_home_dir =

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

@end example

Be cautious on filesystems where the maximum file-size is 2 GB!

InnoDB is not aware of the OS maximum file-size. On those filesystems

you might want to specify the max size for the datafile:

@example

innodb_data_home_dir =

innodb_data_file_path = /ibdata/ibdata1:100M:autoextend:max:2000M

@end example

must be >= 10 MB.

The combined size of the log files must be < 4G.

If you do not specify @code{innodb_data_home_dir}, then

the default is that InnoDB creates its datafiles to the

@code{datadir} of MySQL. Then you cannot use absolute

file paths in @code{innodb_data_file_path}.

InnoDB forms the directory path to a datafile by textually

catenating @code{innodb_data_home_dir} to a datafile name or

path in @code{innodb_data_file_path},

adding a possible slash or backslash in between if needed.

If the keyword @code{innodb_data_home_dir} is not mentioned

in @file{my.cnf} at all, the default for it is the 'dot'

directory @file{./}

which means the @code{datadir} of MySQL.

When you the first time create an InnoDB database, it

is best that you start the MySQL server from the command

# You can write your other MySQL server options here

# ...

#

innodb_data_home_dir = /

innodb_data_home_dir =

#                                  Datafiles must be able to

#                                  hold your data and indexes

innodb_data_file_path = ibdata/ibdata1:2000M;dr2/ibdata/ibdata2:2000M

innodb_data_file_path = /ibdata/ibdata1:2000M;/dr2/ibdata/ibdata2:2000M

#                                  Set buffer pool size to 50 - 80%

#                                  of your computer's memory, but

#                                  make sure on Linux x86 total

@end example

Note that we have placed the two datafiles on different disks.

The reason for the name @code{innodb_data_file_path} is that

you can also specify paths to your datafiles, and

@code{innodb_data_home_dir} is just textually catenated

before your datafile paths, adding a possible slash or

backslash in between. InnoDB will fill the tablespace

InnoDB will fill the tablespace

formed by the datafiles from bottom up. In some cases it will

improve the performance of the database if all data is not placed

on the same physical disk. Putting log files on a different disk from

@item @strong{Option} @tab @strong{Description}

@item @code{innodb_data_home_dir} @tab

The common part of the directory path for all InnoDB datafiles.

The default for this parameter is the @code{datadir} of MySQL.

If you do not mentioned this option in @file{my.cnf}

the default is the @code{datadir} of MySQL.

You can specify this also as an empty string, in which case you

can use absolute file paths in @code{innodb_data_file_path}.

@item @code{innodb_data_file_path} @tab

Paths to individual datafiles and their sizes. The full directory path

to each datafile is acquired by concatenating innodb_data_home_dir to

be < 4 GB on 32-bit computers.

@item @code{innodb_log_buffer_size} @tab

The size of the buffer which InnoDB uses to write log to the log files

on disk.  Sensible values range from 1M to half the combined size of log

files. A big log buffer allows large transactions to run without a need

on disk.  Sensible values range from 1M to 8M.

A big log buffer allows large transactions to run without a need

to write the log to disk until the transaction commit. Thus, if you have

big transactions, making the log buffer big will save disk I/O.

@item @code{innodb_flush_log_at_trx_commit} @tab