manual.texi:

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

@end example

Suppose you have a Windows NT computer with 128 MB RAM and a

single 10 GB hard disk.

Following is an example of possible configuration parameters in

@file{my.cnf} or @file{my.ini} for InnoDB:

@strong{A simple @file{my.cnf} example.} Suppose you have a computer

with 128 MB RAM and one hard disk. Below is an example of

possible configuration parameters in @file{my.cnf} or

@file{my.ini} for InnoDB. We assume you are running

MySQL-Max-3.23.50 or later, or MySQL-4.0.2 or later.

This example suits most users, both on Unix and Windows,

who do not want to distribute InnoDB datafiles and

log files on several disks. This creates an

auto-extending data file @file{ibdata1} and two InnoDB log files

@file{ib_logfile0} and @file{ib_logfile1} to the

@code{datadir} of MySQL (typically @file{/mysql/data}).

Also the small archived InnoDB log file

@file{ib_arch_log_0000000000} ends up in the @code{datadir}. 

@example

[mysqld]

# You can write your other MySQL server options here

# ...

#

innodb_data_home_dir = c:\ibdata

#                                  Datafiles must be able to

#                                  hold your data and indexes

innodb_data_file_path = ibdata1:2000M;ibdata2:2000M

#                                  Set buffer pool size to 50 - 80%

#                                  of your computer's memory

#                                        Data file(s) must be able to

#                                        hold your data and indexes.

#                                        Make sure 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

set-variable = innodb_buffer_pool_size=70M

set-variable = innodb_additional_mem_pool_size=10M

innodb_log_group_home_dir = c:\iblogs

#                                  .._log_arch_dir must be the same

#                                  as .._log_group_home_dir

innodb_log_arch_dir = c:\iblogs

innodb_log_archive=0

set-variable = innodb_log_files_in_group=3

#                                  Set the log file-size to about

#                                  15% of the buffer pool size

set-variable = innodb_log_file_size=10M

#                                        Set the log file size to about

#                                        25 % of the buffer pool size

set-variable = innodb_log_file_size=20M

set-variable = innodb_log_buffer_size=8M

#                                  Set ..flush_log_at_trx_commit to

#                                  0 if you can afford losing

#                                  a few last transactions 

#                                        Set ..flush_log_at_trx_commit

#                                        to 0 if you can afford losing

#                                        some last transactions 

innodb_flush_log_at_trx_commit=1

set-variable = innodb_file_io_threads=4

set-variable = innodb_lock_wait_timeout=50

@end example

Note that @code{InnoDB} @strong{does not create directories:

you must create them yourself.}

Use the Unix or MS-DOS @code{mkdir} command to create

the data and log group home directories.

Check also that the MySQL server

has @strong{the rights to create files} in the directories you specify.

Note that datafiles must be < 2G in

some filesystems! The combined size of datafiles

must be >= 10 MB.

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

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

prompt. Then InnoDB will print the information about the

database creation to the screen, and you see what is

happening.

@strong{Check that the MySQL server has the rights to create files} in

@code{datadir}. 

Note that datafiles must be < 2G in some file systems!

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

size of datafiles must be >= 10 MB. 

When you for the first time create an InnoDB database, it is

best that you start the MySQL server from the command prompt.

Then InnoDB will print the information about the database

creation to the screen, and you see what is happening.

See below next section what the printout should look like.

For example, in Windows you can start @file{mysqld-max.exe} with: 

@example

your-path-to-mysqld>mysqld-max --standalone --console

your-path-to-mysqld>mysqld-max --console

@end example

For information about what the printout should look like,

see @ref{InnoDB init}.

@strong{Where to put @file{my.cnf} or @file{my.ini} in Windows?}

The rules for Windows are the following:

option to the server:

@code{mysqld --defaults-file=your_path_to_my_cnf}.

Suppose you have a Linux computer with 512 MB RAM and

three 20 GB hard disks (at directory paths @file{`/'},

@file{`/dr2'} and @file{`/dr3'}).

Here is an example of possible configuration parameters

in @file{my.cnf} for

InnoDB:

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. 

@strong{An advanced @file{my.cnf} example.} Suppose you have a Linux computer

with 2 GB RAM and three 60 GB hard disks

(at directory paths @file{/}, @file{/dr2} and

@file{/dr3}). Below is an example of possible

configuration parameters in @file{my.cnf} for InnoDB. 

@strong{Note that InnoDB does not create directories: you

have to create them yourself.} Use the Unix or MS-DOS

@code{mkdir} command to create the data and log group home directories. 

@example

[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

#                                  Set buffer pool size to 50 - 80%

#                                  of your computer's memory, but

#                                  make sure on Linux x86 total

#                                  memory usage is < 2 GB

set-variable = innodb_buffer_pool_size=350M

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

#                                        < 2 GB

set-variable = innodb_buffer_pool_size=1G

set-variable = innodb_additional_mem_pool_size=20M

innodb_log_group_home_dir = /dr3/iblogs

#                                        .._log_arch_dir must be the same

innodb_log_arch_dir = /dr3/iblogs

innodb_log_archive=0

set-variable = innodb_log_files_in_group=3

#                                  Set the log file-size to about

#                                        Set the log file size to about

#                                        15 % of the buffer pool size

set-variable = innodb_log_file_size=50M

set-variable = innodb_log_file_size=150M

set-variable = innodb_log_buffer_size=8M

#                                        Set ..flush_log_at_trx_commit to

#                                        0 if you can afford losing

#                                  a few last transactions 

#                                        some last transactions 

innodb_flush_log_at_trx_commit=1

set-variable = innodb_file_io_threads=4

set-variable = innodb_lock_wait_timeout=50

#innodb_flush_method=fdatasync

#innodb_fast_shutdown=1

#set-variable = innodb_thread_concurrency=5

@end example

@strong{How to tune other @file{mysqld} server parameters?}

Typical values which suit most users are:

@example

skip-locking

set-variable = max_connections=200

set-variable = record_buffer=1M

set-variable = sort_buffer=1M

SELECT * FROM t LOCK IN SHARE MODE;

@end example

@subsubsection How to cope with deadlocks?

Deadlocks are a classic problem in transactional databases,

but they are not dangerous unless they are so frequent

that you cannot run certain transactions at all.

Normally you have to write your applications so

that they are always prepared to re-issue a

transaction if it gets rolled back because of a deadlock. 

InnoDB uses automatic row level locking. You can get

deadlocks even in the case of transactions which just

insert or delete a single row. That is because

these operations are not really 'atomic': they

automatically set locks on the (possibly several) index

records of the row inserted/deleted. 

You can cope with deadlocks and reduce the number of

them with the following tricks: 

@itemize @bullet

@item

Always be prepared to re-issue a transaction if it fails

in a deadlock. Deadlocks are not dangerous. Just try again. 

@item

Commit your transactions often. Small transactions are less

prone to collide. 

@item

Access your tables and rows in a fixed order. Then

transactions will form nice queues, and do not deadlock. 

@item

Use less locking: if you can afford a @code{SELECT} to return

data from an old snapshot, do not add the clause

@code{FOR UPDATE} or @code{LOCK IN SHARE MODE} to it. 

@item

If nothing helps, serialize your transactions with table level

locks: @code{LOCK TABLES t1 WRITE, t2 READ, ... ;

[do something with tables t1 and t2 here]; UNLOCK TABLES.}

Table level locks make you transactions to queue nicely,

and deadlocks are avoided. Note that @code{LOCK TABLES} implicitly

starts a transaction, just like the command @code{BEGIN},

and @code{UNLOCK TABLES} implicitly ends the transaction in a

@code{COMMIT}. 

@end itemize

@subsection Performance Tuning Tips

than half a database page. The maximun key length is 7000 bytes.

@item

On some operating systems datafiles must be < 2 GB. The combined

size of log files must be < 4 GB on 32-bit computers.

size of log files must be < 4 GB.

@item

The maximum tablespace size is 4 billion database pages. This is also

the maximum size for a table. The minimum tablespace size is 10 MB.