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This chapter covers topics that deal with administering a MySQL installation,
such as configuring the server, managing user accounts, and performing backups.
The MySQL server, mysqld, is the main program that does most of the
work in a MySQL installation. The server is accompanied by several related
scripts that perform setup operations when you install MySQL or that are
helper programs to assist you in starting and stopping the server.
This section provides an overview of the server and related programs, and
information about server startup scripts. Information about configuring the
server itself is given in section 5.2 Configuring the MySQL Server.
All MySQL programs take many different options. However, every
MySQL program provides a --help option that you can use
to get a description of the program's options. For example, try
mysqld --help.
You can override default options for all standard programs by specifying
options on the command line or in an option file.
section 4.3 Specifying Program Options.
The following list briefly describes the MySQL server and server-related
programs:
mysqld
-
The SQL daemon (that is, the MySQL server). To use client programs, this
program must be running, because clients gain access to databases by
connecting to the server.
See section 5.2 Configuring the MySQL Server.
mysqld-max
-
A version of the server that includes additional features.
See section 5.1.2 The
mysqld-max Extended MySQL Server.
mysqld_safe
-
A server startup script.
mysqld_safe attempts to start mysqld-max if it exists, and
mysqld otherwise.
See section 5.1.3 The mysqld_safe Server Startup Script.
mysql.server
-
A server startup script.
This script is used on systems that use run directories containing scripts
that start system services for particular run levels. It invokes
mysqld_safe to start the MySQL server.
See section 5.1.4 The mysql.server Server Startup Script.
mysqld_multi
-
A server startup script that can start or stop multiple servers installed
on the system.
See section 5.1.5 The
mysqld_multi Program for Managing Multiple MySQL Servers.
mysql_install_db
-
This script creates the MySQL grant tables with default privileges. It is
usually executed only once, when first installing MySQL on a system.
mysql_fix_privilege_tables
-
This script is used after an upgrade install operation, to update the grant
tables with any changes that have been made in newer versions of MySQL.
There are several other programs that also are run on the server host:
myisamchk
-
A utility to describe, check, optimize, and repair
MyISAM tables.
myisamchk is described in
section 5.6.2 Using myisamchk for Table Maintenance and Crash Recovery.
make_binary_distribution
-
This program makes a binary release of a compiled MySQL. This could be sent
by FTP to `/pub/mysql/Incoming' on
support.mysql.com for the
convenience of other MySQL users.
mysqlbug
-
The MySQL bug reporting script. It can be be used to
send a bug report to the MySQL list. (You can also visit
http://bugs.mysql.com/ to file a bug report online.)
A MySQL-Max server is a version of the mysqld MySQL server that
has been built to include additional features.
The distribution to use depends on your platform:
-
For Windows, the MySQL binary distributions include both the standard server
(
mysqld.exe) and the MySQL-Max server (mysqld-max.exe), so you
need not get a special distribution. Just use a regular Windows
distribution, available at
http://www.mysql.com/downloads/mysql-4.0.html.
See section 2.2.1 Installing MySQL on Windows.
-
For Linux, if you install MySQL using RPM distributions, use the regular
MySQL-server RPM first to install a standard server named
mysqld. Then use the MySQL-Max RPM to install a server named
mysqld-max. The MySQL-Max RPM presupposes that you have
already installed the regular server RPM. See section 2.2.2 Installing MySQL on Linux for more
information on the Linux RPM packages.
-
All other MySQL-Max distributions contain a single server that is named
mysqld but that has the additional features included.
You can find the MySQL-Max binaries on the MySQL AB Web site at
http://www.mysql.com/downloads/mysql-4.0.html.
MySQL AB builds the MySQL-Max servers by using the following
configure options:
--with-server-suffix=-max
-
This option adds a
-max suffix to the mysqld version string.
--with-innodb
-
This option enables support for the
InnoDB storage engine. MySQL-Max
servers always include InnoDB support, but this option actually is
used only for MySQL 3.23 because InnoDB is not included by default
until MySQL 4. From MySQL 4 on, InnoDB is included by default in
binary distributions, so you do not need a MySQL-Max server to obtain
InnoDB support.
--with-bdb
-
This option enables support for the Berkeley DB (
BDB) storage engine.
CFLAGS=-DUSE_SYMDIR
-
This define enables symbolic link support for Windows.
MySQL-Max binary distributions are a convenience for those who wish to install
precompiled programs. If you build MySQL using a source distribution, you can
build your own Max-like server by enabling the same features at configuration
time that the MySQL-Max binary distributions are built with.
MySQL-Max servers include the BerkeleyDB (BDB) storage engine
whenever possible, but not all platforms support BDB. The following
table shows which platforms allow MySQL-Max binaries to include BDB:
| System | BDB Support
|
| AIX 4.3 | N
|
| HP-UX 11.0 | N
|
| Linux-Alpha | N
|
| Linux-IA-64 | N
|
| Linux-Intel | Y
|
| Mac OS X | N
|
| NetWare | N
|
| SCO OSR5 | Y
|
| Solaris-Intel | N
|
| Solaris-SPARC | Y
|
| UnixWare | Y
|
| Windows/NT | Y
|
To find out which storage engines your server supports, issue the following
statement:
mysql> SHOW ENGINES;
Before MySQL 4.1.2, use the following statement instead and check the value
of the variable for the storage engine in which you are interested:
mysql> SHOW VARIABLES LIKE 'have_%';
+------------------+----------+
| Variable_name | Value |
+------------------+----------+
| have_bdb | NO |
| have_crypt | YES |
| have_innodb | YES |
| have_isam | NO |
| have_raid | NO |
| have_symlink | DISABLED |
| have_openssl | NO |
| have_query_cache | YES |
+------------------+----------+
The values in the second column indicate the server's level of support for
each feature:
| Value | Meaning
|
YES | The feature is supported and is active.
|
NO | The feature is not supported.
|
DISABLED | The feature is supported but has been disabled.
|
A value of NO means that the server was compiled without support
for the feature, so it cannot be activated at runtime.
A value of DISABLED occurs either because the server was
started with an option that disables the feature, or because not
all options required to enable it were given. In the latter case, the
hostname.err error log file should contain a reason indicating why
the option is disabled.
One situation in which you might see DISABLED occurs with MySQL 3.23
when the InnoDB storage engine is compiled in. In MySQL 3.23, you
must supply at least the innodb_data_file_path option at runtime to
set up the InnoDB tablespace. Without this option, InnoDB
disables itself.
See section 16.3 InnoDB in MySQL 3.23.
You can specify configuration options for the BDB storage engine, too,
but BDB will not disable itself if you do not provide them.
See section 15.4.3 BDB Startup Options.
You might also see DISABLED for the InnoDB, BDB, or
ISAM storage engines if the server was compiled to support them, but
was started with the --skip-innodb, --skip-bdb, or
--skip-isam options at runtime.
As of Version 3.23, all MySQL servers support MyISAM tables, because
MyISAM is the default storage engine.
mysqld_safe is the recommended way to start a mysqld
server on Unix and NetWare. mysqld_safe adds some safety features
such as restarting the server when an error occurs and logging run-time
information to an error log file. NetWare-specific behaviors are listed
later in this section.
Note:
Before MySQL 4.0, mysqld_safe is named safe_mysqld.
To preserve backward compatibility, MySQL binary distributions for
some time will include safe_mysqld as a symbolic link to
mysqld_safe.
By default, mysqld_safe tries to start an executable named
mysqld-max if it exists, or mysqld otherwise.
Be aware of the implications of this behavior:
-
On Linux, the
MySQL-Max RPM relies on this mysqld_safe
behavior. The RPM installs an executable named mysqld-max, which
causes mysqld_safe to automatically use that executable from that
point on.
-
If you install a MySQL-Max distribution that includes a server named
mysqld-max, then upgrade later to a non-Max version of MySQL,
mysqld_safe will still attempt to run the old mysqld-max
server. If you perform such an upgrade, you should manually remove the old
mysqld-max server to ensure that mysqld_safe runs the new
mysqld server.
To override the default behavior and specify explicitly which server you
want to run, specify a --mysqld or --mysqld-version option to
mysqld_safe..
Many of the options to mysqld_safe are the same as the options to
mysqld. See section 5.2.1 mysqld Command-line Options.
Note that all options specified to mysqld_safe on the command line are
passed to mysqld. If you want to use any options that are specific
to mysqld_safe and that mysqld doesn't support, do not specify
them on the command line. Instead, list in the [mysqld_safe] group
of an option file.
See section 4.3.2 Using Option Files.
mysqld_safe reads all options from the [mysqld],
[server] and [mysqld_safe] sections in option files.
(For backward compatibility, it also reads [safe_mysqld]
sections, though you should rename such sections to [mysqld_safe]
when you begin using MySQL 4.0 or later.)
mysqld_safe supports the following options:
--basedir=path
-
The path to the MySQL installation directory.
--core-file-size=size
-
The size of the core file
mysqld should be able to create. The option
value is passed to ulimit -c.
--datadir=path
-
The path to the data directory.
--defaults-extra-file=path
-
The name of an option file to be read in addition to the usual option files.
--defaults-file=path
-
The name of an option file to be read instead of the usual option files.
--err-log=path
-
The old form of the
--log-error option, to be used before MySQL 4.0.
--ledir=path
-
The path to the directory containing the
mysqld program.
Use this option to explicitly indicate the location of the server.
--log-error=path
-
Write the error log to the given file. See section 5.8.1 The Error Log.
--mysqld=prog_name
-
The name of the server program (in the
ledir directory) that you
want to start.
--mysqld-version=suffix
-
This option is similar to the
--mysqld option, but you specify only
the suffix for the server program name. The basename is assumed to be
mysqld. For example, if you use --mysqld-version=max,
mysqld_safe will start the mysqld-max program in the
ledir directory. If the argument to --mysqld-version is
empty, mysqld_safe uses mysqld in the ledir directory.
--nice=priority
-
Use the
nice program to set the server's scheduling priority to the
given value. This option was added in MySQL 4.0.14.
--no-defaults
-
Do not read any option files.
--open-files-limit=count
-
The number of files
mysqld should be able to open. The option value
is passed to ulimit -n. Note that you need to start
mysqld_safe as root for this to work properly!
--pid-file=path
-
The path to the process ID file.
--port=port_num
-
The port number to use when listening for TCP/IP connections.
--socket=path
-
The Unix socket file to use for local connections.
--timezone=zone
-
Set the
TZ time zone environment variable to the given option value.
Consult your operating system documentation for legal time zone
specification formats.
--user={user_name | user_id}
-
Run the
mysqld server as the user having the name user_name or
the numeric user ID user_id.
(``User'' in this context refers to a system login account, not a MySQL user
listed in the grant tables.)
The mysqld_safe script is written so that it normally can start a
server that was installed from either a source or a binary distribution of
MySQL, even though these types of distributoins typically install the server
in slightly different locations.
(See section 2.1.8 Installation Layouts.)
mysqld_safe expects one of the following conditions to be true:
-
The server and databases can be found relative to the directory from which
mysqld_safe is invoked. For binary distributions, mysqld_safe
looks under its working directory for `bin' and `data'
directories. For source distributions, it looks for `libexec' and
`var' directories. This condition should be met if you execute
mysqld_safe from your MySQL installation directory (for example,
`/usr/local/mysql' for a binary distribution).
-
If the server and databases cannot be found relative to the working
directory,
mysqld_safe attempts to locate them by absolute pathnames.
Typical locations are `/usr/local/libexec' and `/usr/local/var'.
The actual locations are determined from the values configured into the
distribution at the time it was built. They should be correct if MySQL
is installed in the location specified at configuration time.
Because mysqld_safe will try to find the server and databases relative
to its own working directory, you can install a binary distribution of
MySQL anywhere, as long as you run mysqld_safe from the
MySQL installation directory:
shell> cd mysql_installation_directory
shell> bin/mysqld_safe &
If mysqld_safe fails, even when invoked from the MySQL
installation directory, you can specify the --ledir and
--datadir options to indicate the directories in which the server and
databases are located on your system.
Normally, you should not edit the mysqld_safe script. Instead,
configure mysqld_safe by using command-line options or options in the
[mysqld_safe] section of a `my.cnf' option file. In rare cases,
it might be necessary to edit mysqld_safe to get it to start the server
properly. However, if you do this, your modified version of
mysqld_safe might be overwritten if you upgrade MySQL in the future, so
you should make a copy of your edited version that you can reinstall.
On NetWare, mysqld_safe is a NetWare Loadable Module (NLM) that is
ported from the original Unix shell script. It does the following:
-
Runs a number of system and option checks.
-
Runs a check on
MyISAM and ISAM tables.
-
Provides a screen presence for the MySQL server.
-
Starts
mysqld, monitors it, and restarts it if it terminates in error.
-
Sends error messages from
mysqld to the `hostname.err' file in the
data directory.
-
Sends
mysqld_safe screen output to the `hostname.safe' file in the
data directory.
MySQL distributions on Unix include a script named mysql.server.
It can be used on systems such as Linux and Solaris that use System V-style
run directories to start and stop system services. It is also used by the Mac
OS X Startup Item for MySQL.
mysql.server can be found in the `support-files' directory under
your MySQL installation directory or in a MySQL source tree.
Note that if you use the Linux server RPM package
(MySQL-server-VERSION.rpm), the mysql.server script will
already have been installed in the `/etc/init.d' directory with the
name `mysql'. You need not install it manually. See
section 2.2.2 Installing MySQL on Linux for more information on the Linux RPM packages.
If you install MySQL from a source distribution or using a binary distribution
format that does not install mysql.server automatically, you can
install it manually. Instructions are provided in section 2.4.2.2 Starting and Stopping MySQL Automatically.
mysql.server reads options from the [mysql.server] and
[mysqld] sections of option files. (For backward compatibility,
it also reads [mysql_server] sections, though you should rename such
sections to [mysql.server] when you begin using MySQL 4.0 or later.)
mysqld_multi is meant for managing several mysqld
processes that listen for connections on different Unix socket files and
TCP/IP ports. It can start or stop servers, or report their current status.
The program searches for groups named [mysqld#] in `my.cnf' (or
in the file named by the --config-file option). # can be any
positive integer. This number is referred to in the following discussion as
the option group number, or GNR. Group numbers distinquish option groups
from one another and are used as arguments to mysqld_multi to specify
which servers you want to start, stop, or obtain a status report for.
Options listed in these groups are the same that you would use in the
[mysqld] group used for starting mysqld. (See, for example,
section 2.4.2.2 Starting and Stopping MySQL Automatically.) However, when using multiple servers it is necessary
that each one use its own value for options such as the Unix socket file and
TCP/IP port number. For more information on which options must be unique per
server in a multiple-server environment, see section 5.9 Running Multiple MySQL Servers on the Same Machine.
To invoke mysqld_multi, use the following syntax:
shell> mysqld_multi [options] {start|stop|report} [GNR[,GNR]...]
start, stop, and report indicate which operation you
want to perform. You can perform the designated operation on a single server
or multiple servers, depending on the GNR list that follows the option name.
If there is no list, mysqld_multi performs the operation for all
servers in the option file.
Each GNR value represents an option group number or range of group numbers.
The value should be the number at the end of the group name in the
option file. For example, the GNR for a group named [mysqld17]
is 17. To specify a range of numbers, separate the first and last
numbers by a dash. The GNR value 10-13 represents groups
[mysqld10] through [mysqld13]. Multiple groups or group
ranges can be specified on the command line, separated by commas. There
must be no whitespace characters (spaces or tabs) in the GNR list; anything
after a whitespace character is ignored.
This command starts a single server using option group [mysqld17]:
shell> mysqld_multi start 17
This command stops several servers, using option groups [mysql8]
and [mysqld10] through [mysqld13]:
shell> mysqld_multi start 8,10-13
For an example of how you might set up an option file, use this command:
shell> mysqld_multi --example
mysqld_multi supports the following options:
--config-file=name
-
Specify the name of an alternative option file. This affects where
mysqld_multi looks for [mysqld#] option groups. Without this
option, all options are read from the usual `my.cnf' file. The option
does not affect where mysqld_multi reads its own options, which are
always taken from the [mysqld_multi] group in the usual `my.cnf'
file.
--example
-
Display an example option file.
--help
-
Display a help message and exit.
--log=name
-
Specify the name of the log file. If the file exists, log output is appended
to it.
--mysqladmin=prog_name
-
The
mysqladmin binary to be used to stop servers.
--mysqld=prog_name
-
The
mysqld binary to be used. Note that you can specify
mysqld_safe as the value for this option also. The options are passed
to mysqld. Just make sure you have the directory where mysqld is
located in your PATH
environment variable setting or fix mysqld_safe.
--no-log
-
Print log information to stdout rather than to the log file. By default,
output goes to the log file.
--password=password
-
The password of the MySQL account to use when invoking
mysqladmin.
Note that the password value is not optional for this option, unlike for other MySQL clients.
--tcp-ip
-
Connect to each MySQL server via the TCP/IP port instead of the Unix socket
file. (If a socket file is missing, the server might still be running,
but accessible only via the TCP/IP port.) By default, connections are
made using the Unix socket file. This option affects
stop and
report operations.
--user=user_name
-
The username of the MySQL account to use when invoking
mysqladmin.
--version
-
Display version information and exit.
Some notes about mysqld_multi:
-
Make sure that the MySQL account used for stopping the
mysqld servers
(with the mysqladmin program) has the same username and password for
each server. Also, make sure that the account has the SHUTDOWN
privilege. If the servers that you want to manage have many different
usernames or passwords for the administrative accounts, you might want to
create an account on each server that has the same username and password.
For example, you might set up a common multi_admin account by
executing the following commands for each server:
shell> mysql -u root -S /tmp/mysql.sock -proot_password
mysql> GRANT SHUTDOWN ON *.*
-> TO 'multi_admin'@'localhost' IDENTIFIED BY 'multipass';
See section 5.4.2 How the Privilege System Works.
You will have to do this for each mysqld server. Change the
connection parameters appropriately when connecting to each one. Note that
the host part of the account name must allow you to connect as
multi_admin from the host where you want to run mysqld_multi.
-
The
--pid-file option is very important if you are using mysqld_safe
to start mysqld (for example, --mysqld=mysqld_safe) Every
mysqld should have its own process ID file. The advantage of
using mysqld_safe instead of mysqld is
that mysqld_safe ``guards'' its mysqld process and will
restart it if the process terminates due to a signal
sent using kill -9, or for other reasons such as a segmentation
fault. Please note that the
mysqld_safe script might require that you start it from a certain
place. This means that you might have to change location to a certain directory
before running mysqld_multi. If you have problems starting,
please see the mysqld_safe script. Check especially the lines:
----------------------------------------------------------------
MY_PWD=`pwd`
# Check if we are starting this relative (for the binary release)
if test -d $MY_PWD/data/mysql -a -f ./share/mysql/english/errmsg.sys -a \
-x ./bin/mysqld
----------------------------------------------------------------
See section 5.1.3 The mysqld_safe Server Startup Script.
The test performed by these lines should be successful, or you might encounter
problems.
-
The Unix socket file and the TCP/IP port must be different for every
mysqld.
-
You might want to use the
--user option for mysqld, but in order
to do this you need to run the mysqld_multi script as the Unix
root user. Having the option in the option file doesn't matter; you
will just get a warning, if you are not the superuser and the mysqld
processes are started under your own Unix account. Important: Make
sure that the data directory is fully accessible to the Unix account that
the specific mysqld process is started as. Do not use the
Unix root account for this, unless you know what you are doing.
-
Most important: Before using
mysqld_multi be sure that you
understand the meanings of the options that are passed to the mysqld
servers and why you would want to have separate mysqld
processes. Beware of the dangers of using multiple mysqld servers
with the same data directory. Use separate data directories, unless you
know what you are doing. Starting multiple servers with the same
data directory will not give you extra performance in a threaded
system.
See section 5.9 Running Multiple MySQL Servers on the Same Machine.
The following example shows how you might set up an option file for use with
mysqld_multi. The first and fifth [mysqld#] group were
intentionally left out from the example to illustrate that you can have
``gaps'' in the option file. This gives you more flexibility. The order in
which the mysqld programs are started or stopped depends on the order
in which they appear in the option file.
# This file should probably be in your home dir (~/.my.cnf)
# or /etc/my.cnf
# Version 2.1 by Jani Tolonen
[mysqld_multi]
mysqld = /usr/local/bin/mysqld_safe
mysqladmin = /usr/local/bin/mysqladmin
user = multi_admin
password = multipass
[mysqld2]
socket = /tmp/mysql.sock2
port = 3307
pid-file = /usr/local/mysql/var2/hostname.pid2
datadir = /usr/local/mysql/var2
language = /usr/local/share/mysql/english
user = john
[mysqld3]
socket = /tmp/mysql.sock3
port = 3308
pid-file = /usr/local/mysql/var3/hostname.pid3
datadir = /usr/local/mysql/var3
language = /usr/local/share/mysql/swedish
user = monty
[mysqld4]
socket = /tmp/mysql.sock4
port = 3309
pid-file = /usr/local/mysql/var4/hostname.pid4
datadir = /usr/local/mysql/var4
language = /usr/local/share/mysql/estonia
user = tonu
[mysqld6]
socket = /tmp/mysql.sock6
port = 3311
pid-file = /usr/local/mysql/var6/hostname.pid6
datadir = /usr/local/mysql/var6
language = /usr/local/share/mysql/japanese
user = jani
See section 4.3.2 Using Option Files.
This section discusses MySQL server configuration topics:
-
Startup options that the server supports
-
How to set the server SQL mode
-
Server system variables
-
Server status variables
When you start the mysqld server, you can specify program options
using any of the methods described in section 4.3 Specifying Program Options. The most
common methods are to provide options in an option file or on the command
line. However, in most cases it is desirable to make sure the server uses
the same options each time it runs. The best way to ensure this is to
list them in an option file.
See section 4.3.2 Using Option Files.
mysqld reads options from the [mysqld] and [server]
groups. mysqld_safe reads options from the [mysqld],
[server], [mysqld_safe] and [safe_mysqld]
groups. mysql.server reads options from the [mysqld]
and [mysql.server] groups. An embedded MySQL server usually reads
options from the [server], [embedded] and [xxxxx_SERVER]
groups, where xxxxx is the name of the application into which the
server is embedded.
mysqld accepts many command-line options.
For a list, execute mysqld --help. Before MySQL 4.1.1, --help
prints the full help message. As of 4.1.1, it prints a brief message; to see
the full list, use mysqld --verbose --help.
The following list shows some of the most common server options.
Additional options are described elsewhere:
You can also set the value of a server system variable by using the variable
name as an option, as described later in this section.
--help, -?
-
Display a short help message and exit.
Before MySQL 4.1.1,
--help displays the full help message.
As of 4.1.1, it displays an abbreviated message only. Use both the
--verbose and --help options to see the full message.
--ansi
-
Use standard SQL syntax instead of MySQL syntax. See section 1.8.3 Running MySQL in ANSI Mode.
For more precise control over the server SQL mode, use the
--sql-mode
option instead.
--basedir=path, -b path
-
The path to the MySQL installation directory. All paths are usually resolved
relative to this.
--big-tables
-
Allow large result sets by saving all temporary sets on file. This option
prevents most ``table full'' errors, but also slows down queries for which
in-memory tables would suffice. Since Version 3.23.2, MySQL is able to
handle large result sets automatically by using memory for small temporary
tables and switching to disk tables where necessary.
--bind-address=IP
-
The IP address to bind to.
--console
-
Write the error log messages to stderr/stdout even if
--log-error
is specified. On Windows, mysqld will not close the console screen if
this option is used.
--character-sets-dir=path
-
The directory where character sets are installed. See section 5.7.1 The Character Set Used for Data and Sorting.
--chroot=path
-
Put the
mysqld server in a closed environment during startup by using the
chroot() system call. This is a recommended security measure as of
MySQL 4.0. (MySQL 3.23 is not able to provide a chroot() jail that is
100% closed.) Note that use of this option somewhat limits LOAD
DATA INFILE and SELECT ... INTO OUTFILE.
--core-file
-
Write a core file if
mysqld dies. For some systems, you must also
specify the --core-file-size option to mysqld_safe.
See section 5.1.3 The mysqld_safe Server Startup Script.
Note that on some systems, such as Solaris, you will
not get a core file if you are also using the --user option.
--datadir=path, -h path
-
The path to the data directory.
--debug[=debug_options], -# [debug_options]
-
If MySQL is configured with
--with-debug, you can use this
option to get a trace file of what mysqld is doing.
The debug_options string often is 'd:t:o,filename'.
See section D.1.2 Creating Trace Files.
--default-character-set=charset
-
Use
charset as the default character set. See section 5.7.1 The Character Set Used for Data and Sorting.
--default-collation=collation
-
Use
collation as the default collation.
This option is available as of MySQL 4.1.1.
See section 5.7.1 The Character Set Used for Data and Sorting.
--default-storage-engine=type
-
This option is a synonym for
--default-table-type.
It is available as of MySQL 4.1.2.
--default-table-type=type
-
Set the default table type for tables. See section 15 MySQL Storage Engines and Table Types.
--delay-key-write[= OFF | ON | ALL]
-
How the
DELAYED KEYS option should be used.
Delayed key writing causes key buffers not to be flushed between writes for
MyISAM tables.
OFF disables delayed key writes.
ON enables delayed key writes for those tables that were created with
the DELAYED KEYS option.
ALL delays key writes for all MyISAM tables.
Available as of MySQL 4.0.3.
See section 7.5.2 Tuning Server Parameters. See section 15.1.1 MyISAM Startup Options.
NOTE: If you set this variable to ALL, you should not use
MyISAM tables from another program (like from another MySQL server or
with myisamchk) when the table is in use. Doing so, will lead to index
corruption.
--delay-key-write-for-all-tables
-
Old form of
--delay-key-write=ALL for use prior to MySQL 4.0.3.
As of 4.0.3, use --delay-key-write instead.
--des-key-file=file_name
-
Read the default keys used by
DES_ENCRYPT() and DES_DECRYPT()
from this file.
--enable-external-locking
-
Enable system locking. Note that if you use this option on a system on
which
lockd does not fully work (as on Linux), you will easily get
mysqld to deadlock.
This option previously was named --enable-locking.
NOTE: If you use this option to enable updates to MyISAM
tables from many MySQL processes, you have to ensure that these conditions are
satisfied:
-
You should not use the query cache for queries that uses tables that are
updated by another process.
-
You should not use
--delay-key-write=ALL or DELAY_KEY_WRITE=1
on any shared tables.
The easiest way to ensure this is to always use --enable-locking
together with --delay-key-write=OFF --query-cache-size=0.
(This is not done by default as in many setups it's useful to have a mixture
of the above options).
--enable-named-pipe
-
Enable support for named pipes.
This option applies only on Windows NT, 2000, and XP systems, and can be used
only with the
mysqld-nt and mysqld-max-nt servers that support
named pipe connections.
--exit-info, -T
-
This is a bit mask of different flags you can use for debugging the
mysqld server. Do not use this option unless you know
exactly what it does!
--flush
-
Flush all changes to disk after each SQL statement. Normally MySQL
only does a write of all changes to disk after each SQL statement and lets
the operating system handle the syncing to disk.
See section A.4.1 What to Do if MySQL Keeps Crashing.
--init-file=file
-
Read SQL statements from this file at startup.
Each statement must be on a single line and should not include comments.
--language=lang_name, -L lang_name
-
Client error messages in given language.
lang_name can be given as the
language name or as the full pathname to the directory where the language
files are installed.
See section 5.7.2 Setting the Error Message Language.
--log[=file], -l [file]
-
Log connections and queries to this file. See section 5.8.2 The General Query Log. If you don't
specify a file name, MySQL will use
hostname.log as filename.
--log-bin=[file]
-
Log all queries that change data to this file. Used for backup and
replication. See section 5.8.4 The Binary Log. If you don't specify a file name,
MySQL will use
hostname-bin as filename.
--log-bin-index[=file]
-
The index file for binary log file names. See section 5.8.4 The Binary Log.
If you don't specify file name, MySQL will use
hostname-bin.index as
filename.
--log-error[=file]
-
Log errors and startup messages to this file. See section 5.8.1 The Error Log.
If you don't specify file name, MySQL will use
hostname.err as filename.
--log-isam[=file]
-
Log all
ISAM/MyISAM changes to this file (used only when
debugging ISAM/MyISAM).
--log-long-format
-
Log some extra information to the log files (update log, binary update log,
and slow queries log, whatever log has been activated). For example,
username and timestamp are logged for queries. If you are using
--log-slow-queries and --log-long-format, then
queries that are not using indexes also are logged to the slow query log.
Note that --log-long-format is deprecated as of MySQL version
4.1, when --log-short-format was introduced (the long log format
is the default setting since version 4.1). Also note that starting with
MySQL 4.1 the --log-queries-not-using-indexes option is available
for the purpose of logging queries that do not use indexes to the slow
queries log.
--log-queries-not-using-indexes
-
If you are using this option with
--log-slow-queries, then also
queries that are not using indexes are logged to the slow query log. This
option is available as of MySQL 4.1. See section 5.8.5 The Slow Query Log.
--log-short-format
-
Log less information to the log files (update log, binary update log,
and slow queries log, whatever log has been activated). For example,
username and timestamp are not logged for queries. This options was
introduced in MySQL 4.1.
--log-slow-queries[=file]
-
Log all queries that have taken more than
long_query_time seconds
to execute to file. Note that the default for the amount of information
logged has changed in MySQL 4.1. See the --log-long-format and
--log-long-format options for details. See section 5.8.5 The Slow Query Log.
--log-update[=file]
-
Log updates to
file.# where # is a unique number if not
given. See section 5.8.3 The Update Log. The update log is deprecated and is
removed in MySQL 5.0.0; you should use the binary log instead
(--log-bin). See section 5.8.4 The Binary Log. Starting from version 5.0.0,
using --log-update will just turn on the binary log instead
(see section C.1.2 Changes in release 5.0.0 (22 Dec 2003: Alpha)).
--log-warnings, -W
-
Print out warnings like
Aborted connection... to the
`.err' file. Enabling this option is recommended, for example, if you
use replication (you will get more information about what is happening,
such as messages about network failures and reconnections). See section A.2.11 Communication Errors / Aborted Connection.
This option was named --warnings before MySQL 4.0.
--low-priority-updates
-
Table-modifying operations (
INSERT/DELETE/UPDATE)
will have lower priority than selects. It can also be done via
{INSERT | REPLACE | UPDATE | DELETE} LOW_PRIORITY ... to lower
the priority of only one query, or by
SET LOW_PRIORITY_UPDATES=1 to change the priority in one
thread. See section 7.3.2 Table Locking Issues.
--memlock
-
Lock the
mysqld process in memory. This works on systems such as
Solaris that support the mlockall() system call. This
might help if you have a problem where the operating system is causing
mysqld to swap on disk.
Note that use of this option requires that you run the server as root,
which is normally not a good idea for security reasons.
--myisam-recover [=option[,option...]]]
-
Set the
MyISAM storage engine recovery mode.
The option value is any combination of the values
of DEFAULT, BACKUP, FORCE or QUICK.
If you specify multiple values, seprate them by commas.
You can also use a value of "" to disable this
option. If this option is used, mysqld will on open check if the
table is marked as crashed or if the table wasn't closed properly.
(The last option works only if you are running with
--skip-external-locking.) If this is the case mysqld will run
check on the table. If the table was corrupted, mysqld will
attempt to repair it.
The following options affect how the repair works:
| Option | Description
|
DEFAULT | The same as not giving any option to
--myisam-recover.
|
BACKUP | If the data table was changed during recover, save a
backup of the `tbl_name.MYD' datafile as
`tbl_name-datetime.BAK'.
|
FORCE | Run recovery even if we will lose more than one row
from the `.MYD' file.
|
QUICK | Don't check the rows in the table if there aren't any
delete blocks.
|
Before a table is automatically repaired, MySQL will add a note
about this in the error log. If you want to be able to recover from most
problems without user intervention, you should use the options
BACKUP,FORCE. This will force a repair of a table even if some rows
would be deleted, but it will keep the old datafile as a backup so that
you can later examine what happened.
--new
-
From version 4.0.12, the
--new option can be used to make the server
behave as 4.1 in certain respects, easing a 4.0 to 4.1 upgrade:
-
TIMESTAMP is returned as a string with the format
'YYYY-MM-DD HH:MM:SS'.
See section 12 Column Types.
This option can be used to help you see how your applications will behave in
MySQL 4.1, without actually upgrading to 4.1.
--pid-file=path
-
The path to the process ID file used by
mysqld_safe.
--port=num, -P num
-
The port number to use when listening for TCP/IP connections.
--old-protocol, -o
-
Use the 3.20 protocol for compatibility with some very old clients.
See section 2.5.6 Upgrading from Version 3.20 to 3.21.
--one-thread
-
Only use one thread (for debugging under Linux).
This option is available only if the server is built with debugging enabled.
See section D.1 Debugging a MySQL server.
--open-files-limit=
-
To change the number of file descriptors available to
mysqld.
If this is not set or set to 0, then mysqld will use this value
to reserve file descriptors to use with setrlimit(). If this
value is 0 then mysqld will reserve max_connections*5 or
max_connections + table_cache*2 (whichever is larger) number of
files. You should try increasing this if mysqld gives you the
error 'Too many open files'.
--safe-mode
-
Skip some optimize stages.
--safe-show-database
-
With this option, the
SHOW DATABASES statement returns only those
databases for which the user has some kind of privilege.
From version 4.0.2 this option is deprecated and doesn't do anything
(the option is enabled by default) as we now have the
SHOW DATABASES privilege. See section 14.5.1.2 GRANT and REVOKE Syntax.
--safe-user-create
-
If this is enabled, a user can't create new users with the
GRANT
statement, if the user doesn't have INSERT privilege to the
mysql.user table or any column in this table.
--skip-bdb
-
Disable the
BDB storage engine. This saves memory and might speed
up some operations.
Do not use this operation if you require BDB tables.
--skip-concurrent-insert
-
Turn off the ability to select and insert at the same time on
MyISAM
tables. (This is only to be used if you think you have found a bug in this
feature.)
--skip-delay-key-write
-
Ignore the
DELAY_KEY_WRITE option for all tables.
As of MySQL 4.0.3, you should use --delay-key-write=OFF instead.
See section 7.5.2 Tuning Server Parameters.
--skip-external-locking
-
Don't use system locking. To use
isamchk or myisamchk you must
shut down the server. See section 1.2.3 MySQL Stability. Note that in MySQL Version
3.23, you can use CHECK TABLE and REPAIR TABLE to check and
repair MyISAM tables.
This option previously was named --skip-locking.
--skip-grant-tables
-
This option causes the server not to use the privilege system at all. This
gives everyone full access to all databases! (You can tell a running
server to start using the grant tables again by executing a
mysqladmin
flush-privileges or mysqladmin reload command, or by issuing a
FLUSH PRIVILEGES statement.)
--skip-host-cache
-
Do not use the internal hostname cache for faster name-IP resolution. Instead,
query the DNS server every time a client connects. See section 7.5.5 How MySQL uses DNS.
--skip-innodb
-
Disable the
InnoDB storage engine. This saves memory and disk
space and might speed up some operations.
Do not use this operation if you require InnoDB tables.
--skip-isam
-
Disable the
ISAM storage engine. As of MySQL 4.1, ISAM is
disabled by default, so this option applies only if the server was configured
with support for ISAM.
This option was added in MySQL 4.1.1.
--skip-name-resolve
-
Do not resolve hostnames when checking client connections. Use only IP
numbers. If you use this option, all
Host column values in the
grant tables must be IP numbers or localhost. See section 7.5.5 How MySQL uses DNS.
--skip-networking
-
Don't listen for TCP/IP connections at all. All interaction with
mysqld must be made via named pipes (on Windows) or Unix socket files
(on Unix). This option is highly recommended for systems where only local
clients are allowed. See section 7.5.5 How MySQL uses DNS.
--skip-new
-
Don't use new, possibly wrong routines.
--skip-symlink
-
This is the old form of
--skip-symbolic-links, for use before MySQL
4.0.13.
--symbolic-links, --skip-symbolic-links
-
Enable or disable symbolic link support. This option has different effects on
Windows and Unix:
-
On Windows, enabling symbolic links allows you to establish a symbolic
link to a database directory by creating a
directory.sym file that contains the path to the real directory.
See section 7.6.1.3 Using Symbolic Links for Databases on Windows.
-
On Unix, enabling symbolic links means that you can link a
MyISAM index file or datafile to another directory with
the INDEX DIRECTORY or DATA DIRECTORY options of the
CREATE TABLE statement. If you delete or rename the table,
the files that its symbolic links point to also are deleted or
renamed. See section 14.2.5 CREATE TABLE Syntax.
This option was added in MySQL 4.0.13.
--skip-safemalloc
-
If MySQL is configured with
--with-debug=full, all MySQL programs
checks for memory overruns during each memory allocation and memory
freeing operation. This checking is very slow, so for the server you
can avoid it when you don't need it by using the --skip-safemalloc
option.
--skip-show-database
-
Don't allow the
SHOW DATABASES statement, unless the user has the
SHOW DATABASES privilege.
--skip-stack-trace
-
Don't write stack traces. This option is useful when you are running
mysqld under a debugger. On some systems, you also must use
this option to get a core file. See section D.1 Debugging a MySQL server.
--skip-thread-priority
-
Disable using thread priorities for faster response time.
--socket=path
-
On Unix, this option specifies the Unix socket file to
use for local connections. The default value is `/tmp/mysql.sock'.
On Windows, the option specifies the pipe name to use for local connections
that use a named pipe. The default value is
MySQL.
--sql-mode=value[,value[,value...]]
-
Set the SQL mode for MySQL. See section 1.8.2 Selecting SQL Modes. This option was added in 3.23.41.
--temp-pool
-
This option causes most temporary files created by the
server to use a small set of names, rather than a unique name for
each new file. This works around a problem in the Linux kernel
dealing with creating many
new files with different names. With the old behavior, Linux seems to
``leak'' memory, as it's being allocated to the directory entry cache
rather than to the disk cache.
--transaction-isolation=level
-
Sets the default transaction isolation level, which can be
READ-UNCOMMITTED,
READ-COMMITTED,
REPEATABLE-READ, or
SERIALIZABLE.
See section 14.4.6 SET TRANSACTION Syntax.
--tmpdir=path, -t path
-
The path of the directory to use for creating temporary files. It might be
useful if your default
/tmp directory resides on a partition that
is too small to hold temporary tables. Starting from MySQL 4.1, this
option accepts several paths that are used in round-robin fashion. Paths
should be separated by colon characters (`:') on Unix and semicolon
characters (`;') on Windows, NetWare, and OS/2.
If the MySQL server is acting as a replication slave, you should not set
--tmpdir to point to a directory on a memory-based filesystem or to a
directory that is cleared when the server host restarts. A replication
slave needs some of its temporary files to survive a machine restart so that
it can replicate temporary tables or LOAD DATA INFILE operations. If
files in the temporary file directory are lost when the server restarts,
replication will fail.
--user={user_name | user_id}, -u {user_name | user_id}
-
Run the
mysqld server as the user having the name user_name or
the numeric user ID user_id.
(``User'' in this context refers to a system login account, not a MySQL user
listed in the grant tables.)
This option is mandatory when starting mysqld as root.
The server will change its user ID during its startup sequence, causing it
to run as that particular user rather than as root.
See section 5.3.1 General Security Guidelines.
Starting from MySQL 3.23.56 and 4.0.12:
To avoid a possible security hole where a user adds a --user=root
option to some `my.cnf' file (thus causing the server to run as
root), mysqld uses only the first
--user option specified and produces a warning if there are multiple
--user options. Options in `/etc/my.cnf' and
`datadir/my.cnf' are processed before
command-line options, so it is recommended that you
put a --user option in `/etc/my.cnf' and specify a value other than
root. The option in `/etc/my.cnf' will be found before any other
--user options, which ensures that the server runs as a user other
than root, and that a warning results if any other --user option
is found.
--version, -V
-
Display version information and exit.
You can assign a value to a server system variables by using an option of
the form --var_name=value. For example, --key_buffer_size=32M
sets the key_buffer_size variable to a value of 32MB.
Note that when setting a variable to a value, MySQL might automatically
correct it to stay within a given range, or adjust the value to the
closest allowable value if only certain values are allowed.
It is also possible to set variables by using
--set-variable=var_name=value or -O var_name=value
syntax. However, this syntax is deprecated as of MySQL 4.0.
You can find a full description for all variables in section 5.2.3 Server System Variables. The section on tuning server parameters includes information
on how to optimize them. See section 7.5.2 Tuning Server Parameters.
You can change the values of most system variables for a running server with the
SET statement. See section 14.5.3.1 SET Syntax.
If you want to restrict the maximum value a startup option can be set to
with SET, you can define this by using the
--maximum-var_name command-line option.
The MySQL server can operate in different SQL modes, and (as of MySQL 4.1)
can apply these
modes differentially for different clients. This allows applications to
tailor server operation to their own requirements.
Modes define what SQL syntax MySQL should support and what kind of data
validation checks it should perform. This makes it easier
to use MySQL in different environments and to use MySQL together
with other database servers.
You can set the default SQL mode by starting mysqld with the
--sql-mode="modes" option. Beginning with MySQL 4.1, you can also
change the mode after startup time by setting the sql_mode variable
with a SET [SESSION|GLOBAL] sql_mode='modes' statement.
Setting the GLOBAL variable affects the operation of all clients that
connect from that time on. Setting the SESSION variable affects only
the current client.
modes is a list of different modes separated by comma (`,')
characters.
You can retrieve the current mode by issuing a SELECT @@sql_mode
statement. The default value is empty (no modes set).
The value also can be empty
(--sql-mode="") if you want to reset it.
The following list describes the supported modes:
ANSI_QUOTES
-
Treat `"' as an identifier quote character (like the MySQL Server
``' quote character) and not as a string quote character. You can still
use ``' to quote identifers in ANSI mode. With
ANSI_QUOTES
enabled, you cannot use double quotes to quote a literal string, because it
will be intepreted as an identifier.
(New in MySQL 4.0.0.)
IGNORE_SPACE
-
Allow spaces between a function name and the `(' character. This forces
all function names to be treated as reserved words. As a result, if you want
to access any database, table, or column name that is a reserved word, you
must quote it. For example, because there is a
USER() function, the
name of the user table in the mysql database and the User
column in that table become reserved, so you must quote them:
SELECT "User" FROM mysql."user";
(New in MySQL 4.0.0.)
NO_AUTO_VALUE_ON_ZERO
-
NO_AUTO_VALUE_ON_ZERO affects handling of AUTO_INCREMENT
columns. Normally, you generate the next sequence number for the column by
inserting either NULL or 0 into it.
NO_AUTO_VALUE_ON_ZERO suppresses this behavior for 0 so that
only NULL generates the next sequence number. This mode can be useful
if 0 has been stored in a table's AUTO_INCREMENT column. (This
is not a recommended practice, by the way.) For example, if you dump the
table with mysqldump and then reload it, normally MySQL generates
new sequence numbers when it encounters the 0 values, resulting in a
table with different contents than the one that was dumped. Enabling
NO_AUTO_VALUE_ON_ZERO before reloading the dump file solves this
problem. (As of MySQL 4.1.1, mysqldump automatically includes
statements in the dump output to enable NO_AUTO_VALUE_ON_ZERO.) (New
in MySQL 4.1.1.)
NO_DIR_IN_CREATE
-
When creating a table, ignore all
INDEX DIRECTORY and DATA
DIRECTORY directives. This option is useful on slave replication servers.
(New in MySQL 4.0.15.)
NO_FIELD_OPTIONS
-
Don't print MySQL field-specific options in the output of
SHOW CREATE
TABLE. This mode is used by mysqldump in portability mode.
(New in MySQL 4.1.1.)
NO_KEY_OPTIONS
-
Don't print MySQL index-specific options in the output of
SHOW CREATE
TABLE. This mode is used by mysqldump in portability mode.
(New in MySQL 4.1.1.)
NO_TABLE_OPTIONS
-
Don't print MySQL table-specific options (such as
ENGINE) in the
output of SHOW CREATE TABLE. This mode is used by mysqldump in
portability mode.
(New in MySQL 4.1.1.)
NO_UNSIGNED_SUBTRACTION
-
In subtraction operations, don't mark the result as
UNSIGNED if one
of the operands is unsigned. Note that this makes UNSIGNED BIGINT not
100% usable in all contexts. See section 13.7 Cast Functions.
(New in MySQL 4.0.2.)
ONLY_FULL_GROUP_BY
-
Don't allow queries which in the
GROUP BY part refers to a not
selected column.
(New in MySQL 4.0.0.)
PIPES_AS_CONCAT
-
Treat
|| as a string concatenation operator (same as CONCAT())
rather than as a synonym for OR.
(New in MySQL 4.0.0.)
REAL_AS_FLOAT
-
Treat
REAL as a synonym for FLOAT rather than as a synonym for
DOUBLE.
(New in MySQL 4.0.0.)
The following special modes are provided as shorthand for combinations of
mode values from the preceding list.
They are available as of MySQL 4.1.1.
ANSI
-
Equivalent to
REAL_AS_FLOAT, PIPES_AS_CONCAT, ANSI_QUOTES, IGNORE_SPACE, ONLY_FULL_GROUP_BY. See section 1.8.3 Running MySQL in ANSI Mode.
DB2
-
Equivalent to
PIPES_AS_CONCAT, ANSI_QUOTES, IGNORE_SPACE, NO_KEY_OPTIONS, NO_TABLE_OPTIONS, NO_FIELD_OPTIONS.
MAXDB
-
Equivalent to
PIPES_AS_CONCAT, ANSI_QUOTES, IGNORE_SPACE, NO_KEY_OPTIONS, NO_TABLE_OPTIONS, NO_FIELD_OPTIONS.
MSSQL
-
Equivalent to
PIPES_AS_CONCAT, ANSI_QUOTES, IGNORE_SPACE, NO_KEY_OPTIONS, NO_TABLE_OPTIONS, NO_FIELD_OPTIONS.
MYSQL323
-
Equivalent to
NO_FIELD_OPTIONS.
MYSQL40
-
Equivalent to
NO_FIELD_OPTIONS.
ORACLE
-
Equivalent to
PIPES_AS_CONCAT, ANSI_QUOTES, IGNORE_SPACE, NO_KEY_OPTIONS, NO_TABLE_OPTIONS, NO_FIELD_OPTIONS.
POSTGRESQL
-
Equivalent to
PIPES_AS_CONCAT, ANSI_QUOTES, IGNORE_SPACE, NO_KEY_OPTIONS, NO_TABLE_OPTIONS, NO_FIELD_OPTIONS.
The server maintains many system variables that indicate how it is configured.
All of them have default values. They can be set at server startup
using options on the command line or in option
files. Most of them can be set at runtime using the
SET statement.
Beginning with MySQL 4.0.3,
the mysqld server maintains two kinds of variables.
Global variables affect the overall operation of the server.
Session variables affect its operation for individual client connections.
When the server starts, it initializes all global variables to their default
values. These defaults can be changed by options specified in option files
or on the command line. After the server starts, those global variables
that are dynamic can be changed by connecting to the server and issuing
a SET GLOBAL var_name statement. To change a global variable,
you must have the SUPER privilege.
The server also maintains a set of session variables for each client
that connects. The client's session variables are initialized at connect
time using the current values of the corresponding global variables. For
those session variables that are dynamic, the client can change them
by issuing a SET SESSION var_name statement. Setting a session
variable requires no special privilege, but a client can change only its
own session variables, not those of any other client.
A change to a global variable is visible to any client that accesses that
global variable. However, it affects the corresponding session variable
that is intialized from the global variable only for clients that connect
after the change. It does not affect the session variable for any client
that is already connected (not even that of the client that issues the
SET GLOBAL statement).
When setting a variable using a startup option, variable values can be given
with a suffix of K, M, or G to indicate kilobytes,
megabytes, or gigabytes. For example, the following command starts the server
with a key buffer size of 16 megabytes:
mysqld --key_buffer_size=16M
Before MySQL 4.0, use this syntax instead:
mysqld --set-variable=key_buffer_size=16M
The lettercase of suffix letters does not matter; 16M and 16m are
equivalent.
At runtime, use the SET statement to set system variables. In this
context, suffix letters cannot be used, but the value can take the form of an
expression:
mysql> SET sort_buffer_size = 10 * 1024 * 1024;
To specify explicitly whether to set the global or session variable, use the
GLOBAL or SESSION options:
mysql> SET GLOBAL sort_buffer_size = 10 * 1024 * 1024;
mysql> SET SESSION sort_buffer_size = 10 * 1024 * 1024;
Without either option, the statement sets the session variable.
The variables that can be set at runtime are listed in
section 5.2.3.1 Dynamic System Variables.
If you want to restrict the maximum value to which a system variable can
be set with the SET statement, you can specify this maximum at
startup by using an option of the form --maximum-var_name at server
startup. For example, to prevent the value of query_cache_size
from being increased to more than 32MB at runtime, use the option
--maximum-query_cache_size=32M. This feature is available as of MySQL
4.0.2.
You can view system variables and their values by using the
SHOW VARIABLES statement. Many variables have both global and
session values. See section 10.4 System Variables for more information.
mysql> SHOW VARIABLES;
+---------------------------------+------------------------------+
| Variable_name | Value |
+---------------------------------+------------------------------|
| back_log | 50 |
| basedir | /usr/local/mysql |
| bdb_cache_size | 8388572 |
| bdb_home | /usr/local/mysql |
| bdb_log_buffer_size | 32768 |
| bdb_logdir | |
| bdb_max_lock | 10000 |
| bdb_shared_data | OFF |
| bdb_tmpdir | /tmp/ |
| bdb_version | Sleepycat Software: ... |
| binlog_cache_size | 32768 |
| bulk_insert_buffer_size | 8388608 |
| character_set | latin1 |
| character_sets | latin1 big5 czech euc_kr |
| concurrent_insert | ON |
| connect_timeout | 5 |
| convert_character_set | |
| datadir | /usr/local/mysql/data/ |
| default_week_format | 0 |
| delay_key_write | ON |
| delayed_insert_limit | 100 |
| delayed_insert_timeout | 300 |
| delayed_queue_size | 1000 |
| flush | OFF |
| flush_time | 0 |
| ft_boolean_syntax | + -><()~*:""&| |
| ft_max_word_len | 84 |
| ft_min_word_len | 4 |
| ft_query_expansion_limit | 20 |
| ft_stopword_file | (built-in) |
| have_bdb | YES |
| have_innodb | YES |
| have_isam | YES |
| have_openssl | YES |
| have_query_cache | YES |
| have_raid | NO |
| have_symlink | DISABLED |
| init_file | |
| innodb_additional_mem_pool_size | 1048576 |
| innodb_buffer_pool_size | 8388608 |
| innodb_data_file_path | ibdata1:10M:autoextend |
| innodb_data_home_dir | |
| innodb_fast_shutdown | ON |
| innodb_file_io_threads | 4 |
| innodb_flush_log_at_trx_commit | 1 |
| innodb_flush_method | |
| innodb_force_recovery | 0 |
| innodb_lock_wait_timeout | 50 |
| innodb_log_arch_dir | |
| innodb_log_archive | OFF |
| innodb_log_buffer_size | 1048576 |
| innodb_log_file_size | 5242880 |
| innodb_log_files_in_group | 2 |
| innodb_log_group_home_dir | ./ |
| innodb_mirrored_log_groups | 1 |
| innodb_thread_concurrency | 8 |
| interactive_timeout | 28800 |
| join_buffer_size | 131072 |
| key_buffer_size | 16773120 |
| key_cache_age_threshold | 300 |
| key_cache_block_size | 1024 |
| key_cache_division_limit | 100 |
| language | /usr/local/mysql/share/... |
| large_files_support | ON |
| local_infile | ON |
| locked_in_memory | OFF |
| log | OFF |
| log_bin | OFF |
| log_slave_updates | OFF |
| log_slow_queries | OFF |
| log_update | OFF |
| log_warnings | OFF |
| long_query_time | 10 |
| low_priority_updates | OFF |
| lower_case_table_names | 0 |
| max_allowed_packet | 1047552 |
| max_binlog_cache_size | 4294967295 |
| max_binlog_size | 1073741824 |
| max_connect_errors | 10 |
| max_connections | 100 |
| max_delayed_threads | 20 |
| max_error_count | 64 |
| max_heap_table_size | 16777216 |
| max_join_size | 4294967295 |
| max_relay_log_size | 0 |
| max_sort_length | 1024 |
| max_tmp_tables | 32 |
| max_user_connections | 0 |
| max_write_lock_count | 4294967295 |
| myisam_max_extra_sort_file_size | 268435456 |
| myisam_max_sort_file_size | 2147483647 |
| myisam_recover_options | force |
| myisam_repair_threads | 1 |
| myisam_sort_buffer_size | 8388608 |
| net_buffer_length | 16384 |
| net_read_timeout | 30 |
| net_retry_count | 10 |
| net_write_timeout | 60 |
| open_files_limit | 1024 |
| pid_file | /usr/local/mysql/name.pid |
| port | 3306 |
| protocol_version | 10 |
| query_cache_limit | 1048576 |
| query_cache_size | 0 |
| query_cache_type | ON |
| read_buffer_size | 131072 |
| read_rnd_buffer_size | 262144 |
| rpl_recovery_rank | 0 |
| server_id | 0 |
| skip_external_locking | ON |
| skip_networking | OFF |
| skip_show_database | OFF |
| slave_net_timeout | 3600 |
| slow_launch_time | 2 |
| socket | /tmp/mysql.sock |
| sort_buffer_size | 2097116 |
| sql_mode | |
| table_cache | 64 |
| table_type | MYISAM |
| thread_cache_size | 3 |
| thread_stack | 131072 |
| timezone | EEST |
| tmp_table_size | 33554432 |
| tmpdir | /tmp/:/mnt/hd2/tmp/ |
| tx_isolation | READ-COMMITTED |
| version | 4.0.4-beta |
| wait_timeout | 28800 |
+---------------------------------+------------------------------+
Most system variables are described here. InnoDB system variables
are listed at
section 16.5 InnoDB Startup Options.
Values for buffer sizes, lengths, and stack sizes are given in bytes unless
otherwise specified.
Information on tuning these variables can be found in section 7.5.2 Tuning Server Parameters.
The system variables have the following meanings. Variables with no
version indicated have been present since at least MySQL 3.22.
ansi_mode
-
Is
ON if mysqld was started with --ansi.
See section 1.8.3 Running MySQL in ANSI Mode.
This variable was added in MySQL 3.23.6 and removed in 3.23.41.
back_log
-
The number of outstanding connection requests MySQL can have. This
comes into play when the main MySQL thread gets very
many connection requests in a very short time. It then takes some time
(although very little) for the main thread to check the connection and start
a new thread. The
back_log value indicates how many requests can be
stacked during this short time before MySQL momentarily stops
answering new requests. You need to increase this only if you expect a large
number of connections in a short period of time.
In other words, this value is the size of the listen queue for incoming
TCP/IP connections. Your operating system has its own limit on the size
of this queue. The manual page for the Unix listen(2) system
call should have more details. Check your OS documentation for the
maximum value for this variable. Attempting to set back_log
higher than your operating system limit will be ineffective.
basedir
-
The MySQL installation base directory. This variable can be set with the
--basedir option.
bdb_cache_size
-
The size of the buffer that is allocated for caching indexes and rows for
BDB tables. If you don't use BDB tables, you should start
mysqld with --skip-bdb to not waste memory for this cache.
This variable was added in MySQL 3.23.14.
bdb_home
-
The base directory for
BDB tables. This should be assigned the same
value as the datadir variable.
This variable was added in MySQL 3.23.14.
bdb_log_buffer_size
-
The size of the buffer that is allocated for caching indexes and rows for
BDB tables. If you don't use BDB tables, you should set this
to 0 or start mysqld with --skip-bdb to not waste memory for
this cache.
This variable was added in MySQL 3.23.31.
bdb_logdir
-
The directory where the
BDB storage engine writes its log files.
This variable can be set with the --bdb-logdir option.
This variable was added in MySQL 3.23.14.
bdb_max_lock
-
The maximum number of locks you can have active on a
BDB table
(10,000 by default). You should increase this if errors such as the
following occur when you perform long transactions or when mysqld has
to examine many rows to calculate a query:
bdb: Lock table is out of available locks
Got error 12 from ...
This variable was added in MySQL 3.23.29.
bdb_shared_data
-
Is
ON if you are using --bdb-shared-data.
This variable was added in MySQL 3.23.29.
bdb_tmpdir
-
The value of the
--bdb-tmpdir option.
This variable was added in MySQL 3.23.14.
bdb_version
-
The BDB storage engine version.
This variable was added in MySQL 3.23.31.
binlog_cache_size
-
The size of the cache to hold the SQL statements for the binary log during
a transaction. A binary log cache is allocated for each client if the
server supports any transactional storage engines and, starting from MySQL
4.1.2, if the server has binary log enabled (
log-bin option). If you
often use big, multiple-statement transactions, you can increase this to get
more performance.
The Binlog_cache_use and Binlog_cache_disk_use status variables
can be useful for tuning the size of this variable.
This variable was added in MySQL 3.23.29.
See section 5.8.4 The Binary Log.
bulk_insert_buffer_size
-
MyISAM uses a special tree-like cache to make bulk inserts faster for
INSERT ... SELECT, INSERT ... VALUES (...), (...), ..., and
LOAD DATA INFILE. This variable limits
the size of the cache tree in bytes per thread. Setting it to 0
disables this optimization.
Note: This cache is used only when adding data to a non-empty table.
The default value is 8MB.
This variable was added in MySQL 4.0.3.
This variable previously was named myisam_bulk_insert_tree_size.
character_set
-
The default character set.
This variable was added in MySQL 3.23.3, then
removed in MySQL 4.1.1 and replaced by the various
character_set_xxx variables.
character_set_client
-
The character set for statements that arrive from the client.
This variable was added in MySQL 4.1.1.
character_set_connection
-
The character set used for literals that do not have a character set
introducer, for some functions, and for number-to-string conversion.
This variable was added in MySQL 4.1.1.
character_set_database
-
The character set used by the default database.
The server sets this variable whenever the default database changes.
If there is no default database, the variable has the same value as
character_set_server.
This variable was added in MySQL 4.1.1.
character_set_results
-
The character set used for returning query results to the client.
This variable was added in MySQL 4.1.1.
character_set_server
-
This variable was added in MySQL 4.1.1.
character_set_system
-
The character set used by the server for storing identifiers.
The value is always
utf8.
This variable was added in MySQL 4.1.1.
character_sets
-
The supported character sets.
This variable was added in MySQL 3.23.15.
collation_connection
-
This variable was added in MySQL 4.1.1.
collation_database
-
The collation used by the default database.
The server sets this variable whenever the default database changes.
If there is no default database, the variable has the same value as
collation_server.
This variable was added in MySQL 4.1.1.
collation_server
-
This variable was added in MySQL 4.1.1.
concurrent_inserts
-
If
ON (the default), MySQL allows INSERT and SELECT
statements to run concurrently for MyISAM tables that have no free
blocks in the middle. You can turn this option off by starting
mysqld with --safe or --skip-new.
This variable was added in MySQL 3.23.7.
connect_timeout
-
The number of seconds the
mysqld server waits for a connect
packet before responding with Bad handshake.
datadir
-
The MySQL data directory. This variable can be set with the
--datadir option.
default_week_format
-
The default mode value to use for the
WEEK() function.
This variable is available as of MySQL 4.0.14.
delay_key_write
-
This option applies only to
MyISAM tables. It can have one of the
following values to affect handling of the DELAY_KEY_WRITE table
option that can be given in CREATE TABLE statements.
| Option | Description
|
OFF | DELAYED_KEY_WRITE is ignored.
|
ON | MySQL honors the DELAY_KEY_WRITE option
for CREATE TABLE. This is the default value.
|
ALL | All new opened tables are treated as if they were
created with the DELAY_KEY_WRITE option enabled.
|
If DELAY_KEY_WRITE is enabled, this means that the key buffer for
tables with this option are not flushed on every index update, but
only when a table is closed. This will speed up writes on keys a lot,
but if you use this feature, you should add automatic checking of all
MyISAM tables by starting the server with the --myisam-recover
option (for example, --myisam-recover=BACKUP,FORCE).
See section 5.2.1 mysqld Command-line Options. See section 15.1.1 MyISAM Startup Options.
Note that --external-lock doesn't offer any protection against
index corruption for tables that uses delayed key writes.
This variable was added in MySQL 3.23.8.
delayed_insert_limit
-
After inserting
delayed_insert_limit delayed rows, the INSERT
DELAYED handler thread checks whether there are any SELECT
statements pending. If so, it allows them to execute before continuing to
insert delayed rows.
delayed_insert_timeout
-
How long an
INSERT DELAYED handler thread should wait for
INSERT statements before terminating.
delayed_queue_size
-
How many rows to queue when handling
INSERT DELAYED
statements. If the queue becomes full, any client that issues an
INSERT DELAYED statement will wait until there is room in the queue
again.
flush
-
This is
ON if you have started mysqld with the --flush
option.
This variable was added in MySQL 3.22.9.
flush_time
-
If this is set to a non-zero value, all tables will be closed every
flush_time seconds to free up resources and sync unflushed data to
disk. We recommend this option only on Windows 9x or Me, or on systems
with minimal resources available.
This variable was added in MySQL 3.22.18.
ft_boolean_syntax
-
The list of operators supported by boolean full-text searches performed using
IN BOOLEAN MODE.
This variable was added in MySQL 4.0.1.
See section 13.6.1 Boolean Full-text Searches.
The default variable value is '+ -><()~*:""&|'. The rules for
changing the value are as follows:
-
Operator function is determined by position within the string.
-
The replacement value must be fourteen characters.
-
Each character must be an ASCII non-alphanumeric character.
-
Either the first or second character must be a space.
-
No duplicates are allowed except the phrase quoting operators in positions
11 and 12. These two characters are not required to be the same, but they
are the only two that may be.
-
Positions 10, 13, and 14 (which by default are set to `:', `&', and
`|') are reserved for future extensions.
ft_max_word_len
-
The maximum length of the word to be included in a
FULLTEXT index.
This variable was added in MySQL 4.0.0.
Note: FULLTEXT indexes must be rebuilt after changing
this variable.
ft_min_word_len
-
The minimum length of the word to be included in a
FULLTEXT index.
This variable was added in MySQL 4.0.0.
Note: FULLTEXT indexes must be rebuilt after changing
this variable.
ft_query_expansion_limit
-
The number of top matches to use for full-text searches performed using
WITH QUERY EXPANSION.
This variable was added in MySQL 4.1.1.
ft_stopword_file
-
The file from which to read the list of stopwords for full-text searches.
All the words from the file are used; comments are not honored.
By default, a built-in list of stopwords is used (as defined in the
`myisam/ft_static.c' file). Setting this variable to an empty string
(
'') disables stopword filtering. This variable was added in
MySQL 4.0.10.
Note: FULLTEXT indexes must be rebuilt after changing
this variable.
group_concat_max_len
-
The maximum allowed result length for the
GROUP_CONCAT() function.
This variable was added in MySQL 4.1.0.
have_bdb
-
YES if mysqld supports BDB tables. DISABLED
if --skip-bdb is used.
This variable was added in MySQL 3.23.30.
have_innodb
-
YES if mysqld supports InnoDB tables. DISABLED
if --skip-innodb is used.
This variable was added in MySQL 3.23.37.
have_innodb
-
YES if mysqld supports ISAM tables. DISABLED
if --skip-isam is used.
This variable was added in MySQL 3.23.30.
have_raid
-
YES if mysqld supports the RAID option.
This variable was added in MySQL 3.23.30.
have_openssl
-
YES if mysqld supports SSL (encryption) of the client/server
protocol.
This variable was added in MySQL 3.23.43.
init_connect
-
A string to be executed by the server for each client that connects.
The string consists of one or more SQL statements. To specify multiple
statements, separate them by semicolon characters.
This variable was added in MySQL 4.1.2.
For example, each client begins by default with autocommit mode enabled.
There is no global server variable to specify that autocommit should be
disabled by default, but
init_connect can be used to achieve the
same effect:
SET GLOBAL init_connect='SET AUTOCOMMIT=0';
This variable can also be set on the command line or in an option file.
To set the variable as just shown using an option file, include these
lines:
[mysqld]
init_connect='SET AUTOCOMMIT=0'
init_file
-
The name of the file specified with the
--init-file option when you
start the server. This is a file containing SQL statements that you want
the server to execute when it starts.
Each statement must be on a single line and should not include comments.
This variable was added in MySQL 3.23.2.
init_slave
-
This variable is similar to
init_connect, but is a string to be
executed by a slave server each time the SQL thread starts. The format of
the string is the same as for the init_connect variable.
This variable was added in MySQL 4.1.2.
innodb_xxx
-
The
InnoDB system variables are listed at
section 16.5 InnoDB Startup Options.
interactive_timeout
-
The number of seconds the server waits for activity on an interactive
connection before closing it. An interactive client is defined as a
client that uses the
CLIENT_INTERACTIVE option to
mysql_real_connect(). See also wait_timeout.
join_buffer_size
-
The size of the buffer that is used for full joins (joins that do not
use indexes). The buffer is allocated one time for each full join
between two tables. Increase this value to get a faster full join when
adding indexes is not possible. (Normally the best way to get fast joins
is to add indexes.)
key_buffer_size
-
Index blocks for
MyISAM and ISAM tables are buffered and are
shared by all threads. key_buffer_size is the size of the buffer
used for index blocks. The key buffer is also known as the key cache.
Increase the value to get better index handling (for all reads and multiple
writes) to as much as you can afford. Using a value that is 25% of total
memory on a machine that mainly runs MySQL is quite common. However, if you
make the value too large (for example, more than 50% of your total memory)
your system might start to page and become extremely slow. Remember that
MySQL relies on the operating system to perform filesystem caching for data
reads, so you must leave some room for the filesystem cache.
For even more speed when writing many rows at the same time, use
LOCK TABLES. See section 14.4.5 LOCK TABLES and UNLOCK TABLES Syntax.
You can check the performance of the key buffer by issuing a SHOW
STATUS statement and examining the Key_read_requests,
Key_reads, Key_write_requests, and Key_writes status
variables.
See section 14.5.3 SET and SHOW Syntax.
The Key_reads/Key_read_requests ratio should normally be
less than 0.01. The Key_writes/Key_write_requests ratio is usually
near 1 if you are using mostly updates and deletes, but might be much
smaller if you tend to do updates that affect many rows at the same time or
if you are using the DELAY_KEY_WRITE table option.
The fraction of the key buffer in use can be determined using
key_buffer_size in conjunction with the Key_blocks_used status
variable and the buffer blocksize. From MySQL 4.1.1 on, the buffer block
size is available from the key_cache_block_size server variable. The
fraction of the buffer in use is:
(Key_blocks_used * key_cache_block_size) / key_buffer_size
Before MySQL 4.1.1, key cache blocks are 1024 bytes, so the fraction of the
key buffer in use is:
(Key_blocks_used * 1024) / key_buffer_size
See section 7.4.6 The MyISAM Key Cache.
key_cache_age_threshold
-
This value controls the demotion of buffers from the hot sub-chain of a key
cache to the warm sub-chain.
Lower values cause demotion to happen more quickly.
The minimum value is 100.
The default value is 300.
This variable was added in MySQL 4.1.1.
See section 7.4.6 The
MyISAM Key Cache.
key_cache_block_size
-
The size in bytes of blocks in the key cache.
The default value is 1024.
This variable was added in MySQL 4.1.1.
See section 7.4.6 The
MyISAM Key Cache.
key_cache_division_limit
-
The division point between the hot and warm sub-chains of the key cache
buffer chain. The value is the percentage of the buffer chain to use for
the warm sub-chain. Allowable values range from 1 to 100.
The default value is 100.
This variable was added in MySQL 4.1.1.
See section 7.4.6 The
MyISAM Key Cache.
language
-
The language used for error messages.
large_file_support
-
Whether
mysqld was compiled with options for big file support.
This variable was added in MySQL 3.23.28.
local_infile
-
Whether
LOCAL is supported for LOAD DATA INFILE statements.
This variable was added in MySQL 4.0.3.
locked_in_memory
-
Whether
mysqld was locked in memory with --memlock.
This variable was added in MySQL 3.23.25.
log
-
Whether logging of all queries to the general query log is enabled.
See section 5.8.2 The General Query Log.
log_bin
-
Whether the binary log is enabled.
This variable was added in MySQL 3.23.14.
See section 5.8.4 The Binary Log.
log_slave_updates
-
Whether updates received by a slave server from a master server should be
logged to the slave's own binary log. Binary logging must be enabled on the
slave for this to have any effect.
This variable was added in MySQL 3.23.17.
See section 6.8 Replication Startup Options.
log_slow_queries
-
Whether slow queries should be logged. ``Slow'' is determined by the value
of the
long_query_time variable.
This variable was added in MySQL 4.0.2.
See section 5.8.5 The Slow Query Log.
log_update
-
Whether the update log is enabled. This variable was added in MySQL 3.22.18.
Note that the binary log is preferable to the update log, which
is unavailable as of MySQL 5.0.
See section 5.8.3 The Update Log.
long_query_time
-
If a query takes longer than this many seconds, the
Slow_queries counter
is incremented. If you are using the --log-slow-queries option, the query
is logged to the slow query log file. This value is measured in real
time, not CPU time, so a query that is under the threshold on a lightly
loaded system might be above the threshold on a heavily loaded one.
See section 5.8.5 The Slow Query Log.
low_priority_updates
-
If set to
1, all INSERT, UPDATE, DELETE, and
LOCK TABLE WRITE statements wait until there is no pending
SELECT or LOCK TABLE READ on the affected table.
This variable previously was named sql_low_priority_updates.
It was added in MySQL 3.22.5.
lower_case_table_names
-
If set to 1, table names are stored in lowercase on disk and table name
comparisons are not case sensitive. This variable was added in MySQL 3.23.6.
If set to 2 (new in 4.0.18), table names are stored as given but compared
in lowercase. From MySQL 4.0.2, this option also applies to database names.
From 4.1.1, it also applies to table aliases.
See section 10.2.2 Identifier Case Sensitivity.
Note that you should not set this variable to 0 if you are running
MySQL on a system that does not have case-sensitive filenames (such as
Windows or Mac OS X). New in 4.0.18: If this variable is 0 and the
filesystem on which the data directory is located does not have
case-sensitive filenames, MySQL automatically sets
lower_case_table_names to 2.
max_allowed_packet
-
The maximum size of one packet or any generated/intermediate string.
The packet message buffer is initialized to
net_buffer_length
bytes, but can grow up to max_allowed_packet bytes when needed.
This value by default is small, to catch big (possibly wrong) packets.
You must increase this value if you are using big BLOB columns or
long strings. It should be as big as the biggest BLOB you want to
use. The protocol limit for max_allowed_packet is 16MB before
MySQL 4.0 and 1GB thereafter.
max_binlog_cache_size
-
If a multiple-statement transaction requires more than this amount of memory,
you will get the error
Multi-statement transaction required more than
'max_binlog_cache_size' bytes of storage.
This variable was added in MySQL 3.23.29.
max_binlog_size
-
If a write to the binary log exceeds the given value, rotate the binary
logs. You cannot set this variable to more than 1GB or to less than 4096
bytes. (The minimum before MYSQL 4.0.14 is 1024 bytes.) The default value
is 1GB. This variable was added in MySQL 3.23.33.
Note if you are using transactions: A transaction is written in one chunk to
the binary log, hence it is never split between several binary logs.
Therefore, if you have big transactions, you might see binary logs bigger than
max_binlog_size.
If max_relay_log_size is 0, the value of max_binlog_size
applies to relay logs as well. max_relay_log_size was added in
MySQL 4.0.14.
max_connect_errors
-
If there are more than this number of interrupted connections from a host,
that host is blocked from further connections. You can unblock blocked hosts
with the
FLUSH HOSTS statement.
max_connections
-
The number of simultaneous client connections allowed. Increasing this value
increases the number of file descriptors that
mysqld requires. See
section 7.4.8 How MySQL Opens and Closes Tables for comments on file descriptor limits.
See section A.2.7 Too many connections.
max_delayed_threads
-
Don't start more than this number of threads to handle
INSERT DELAYED
statements. If you try to insert data into a new table after all INSERT
DELAYED threads are in use, the row will be inserted as if the
DELAYED attribute wasn't specified. If you set this to 0, MySQL
never creates a thread to handle DELAYED rows; in effect, this
disables DELAYED entirely.
This variable was added in MySQL 3.23.0.
max_error_count
-
The maximum number of error, warning, and note messages to be stored for
display by
SHOW ERRORS or SHOW WARNINGS.
This variable was added in MySQL 4.1.0.
max_heap_table_size
-
This variable sets the maximum size to which
MEMORY (HEAP)
tables are allowed to grow. The value of the variable is used to calculate
MEMORY table MAX_ROWS values. Setting this variable has no
effect on any existing MEMORY table, unless the table is re-created
with a statement such as CREATE TABLE or TRUNCATE TABLE, or
altered with ALTER TABLE.
This variable was added in MySQL 3.23.0.
max_insert_delayed_threads
-
This variable is a synonym for
max_delayed_threads.
It was added in MySQL 4.0.19.
max_join_size
-
Don't allow
SELECT statements that probably will need to examine
more than max_join_size row combinations or are likely to do more
than max_join_size disk seeks. By setting this value, you can catch
SELECT statements where keys are not used properly and that would
probably take a long time. Set it if your users tend to perform joins
that lack a WHERE clause, that take a long time, or that return
millions of rows.
Setting this variable to a value other than DEFAULT resets
the SQL_BIG_SELECTS value to 0. If you set the
SQL_BIG_SELECTS value again, the max_join_size variable
is ignored.
If a query result already is in the query cache, no result size
check is performed, because the result has already been computed and it will
not burden the server to send it to the client.
This variable previously was named sql_max_join_size.
max_relay_log_size
-
If a write by a replication slave to its relay log exceeds the given value,
rotate the relay log. This variable enables you to put different size
constraints on relay logs and binary logs. However, setting the variable to
0 makes MySQL use
max_binlog_ |
