Options that affect security: See Section 5.7.3, “Security-Related mysqld Options”.

SSL-related options: See Section 5.9.7.5, “SSL Command Options”.

Binary log control options: See Section 5.12.3, “The Binary Log”.

Replication-related options: See Section 6.8, “Replication Startup Options”.

Options specific to particular storage engines: See Section 14.1.1, “MyISAM Startup Options”, Section 14.5.3, “BDB Startup Options”, Section 14.2.4, “InnoDB Startup Options and System Variables”, and Section 15.5.5.1, “MySQL Cluster-Related Command Options for mysqld”.

--help, -?

Display a short help message and exit. Use both the --verbose and --help options to see the full message.

--allow-suspicious-udfs

This option controls whether user-defined functions that have only an xxx symbol for the main function can be loaded. By default, the option is off and only UDFs that have at least one auxiliary symbol can be loaded; this prevents attempts at loading functions from shared object files other than those containing legitimate UDFs. This option was added in version 5.0.3. See Section 24.2.4.6, “User-Defined Function Security Precautions”.

--ansi

Use standard (ANSI) SQL syntax instead of MySQL syntax. For more precise control over the server SQL mode, use the --sql-mode option instead. See Section 1.9.3, “Running MySQL in ANSI Mode”, and Section 5.2.5, “The Server SQL Mode”.

--basedir=path, -b path

The path to the MySQL installation directory. All paths are usually resolved relative to this directory.

--bind-address=IP

The IP address to bind to.

--bootstrap

This option is used by the mysql_install_db script to create the MySQL privilege tables without having to start a full MySQL server.

--character-sets-dir=path

The directory where character sets are installed. See Section 5.11.1, “The Character Set Used for Data and Sorting”.

--character-set-client-handshake

Don't ignore character set information sent by the client. To ignore client information and use the default server character set, use --skip-character-set-client-handshake; this makes MySQL behave like MySQL 4.0.

--character-set-filesystem=charset_name

The filesystem character set. This option sets the character_set_filesystem system variable. It was added in MySQL 5.0.19.

--character-set-server=charset_name, -C charset_name

Use charset_name as the default server character set. See Section 5.11.1, “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. Note that use of this option somewhat limits LOAD DATA INFILE and SELECT ... INTO OUTFILE.

--collation-server=collation_name

Use collation_name as the default server collation. See Section 5.11.1, “The Character Set Used for Data and Sorting”.

--console

(Windows only.) Write error log messages to stderr and stdout even if --log-error is specified. mysqld does not close the console window if this option is used.

--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 5.4.1, “mysqld_safe — MySQL Server Startup Script”. Note that on some systems, such as Solaris, you do 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,file_name'. The default is 'd:t:i:o,mysqld.trace'. See Section E.1.2, “Creating Trace Files”.

--default-character-set=charset_name (DEPRECATED)

Use charset_name as the default character set. This option is deprecated in favor of --character-set-server. See Section 5.11.1, “The Character Set Used for Data and Sorting”.

--default-collation=collation_name

Use collation_name as the default collation. This option is deprecated in favor of --collation-server. See Section 5.11.1, “The Character Set Used for Data and Sorting”.

--default-storage-engine=type

Set the default storage engine (table type) for tables. See Chapter 14, Storage Engines and Table Types.

--default-table-type=type

This option is a synonym for --default-storage-engine.

--default-time-zone=timezone

Set the default server time zone. This option sets the global time_zone system variable. If this option is not given, the default time zone is the same as the system time zone (given by the value of the system_time_zone system variable.

--delay-key-write[= OFF | ON | ALL]

Specify how to use delayed key writes. 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 DELAY_KEY_WRITE option. ALL delays key writes for all MyISAM tables. See Section 7.5.2, “Tuning Server Parameters”, and Section 14.1.1, “MyISAM Startup Options”.

Note: If you set this variable to ALL, you should not use MyISAM tables from within another program (such as another MySQL server or myisamchk) when the tables are in use. Doing so leads to index corruption.

--des-key-file=file_name

Read the default DES keys from this file. These keys are used by the DES_ENCRYPT() and DES_DECRYPT() functions.

--enable-named-pipe

Enable support for named pipes. This option applies only on Windows NT, 2000, XP, and 2003 systems, and can be used only with the mysqld-nt and mysqld-max-nt servers that support named-pipe connections.

--exit-info[=flags], -T [flags]

This is a bit mask of different flags that you can use for debugging the mysqld server. Do not use this option unless you know exactly what it does!

--external-locking

Enable external locking (system locking), which is disabled by default as of MySQL 4.0. Note that if you use this option on a system on which lockd does not fully work (such as Linux), it is easy for 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 must ensure that the following conditions are satisfied:

The easiest way to ensure this is to always use --external-locking together with --delay-key-write=OFF and --query-cache-size=0. (This is not done by default because in many setups it is useful to have a mixture of the preceding options.)

--flush

Flush (synchronize) all changes to disk after each SQL statement. Normally, MySQL does a write of all changes to disk only after each SQL statement and lets the operating system handle the synchronizing to disk. See Section A.4.2, “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.

--innodb-safe-binlog

Adds consistency guarantees between the content of InnoDB tables and the binary log. See Section 5.12.3, “The Binary Log”. This option was removed in MySQL 5.0.3, having been made obsolete by the introduction of XA transaction support.

--innodb-xxx

The InnoDB options are listed in Section 14.2.4, “InnoDB Startup Options and System Variables”.

--language=lang_name, -L lang_name

Return client error messages in the 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 5.11.2, “Setting the Error Message Language”.

--large-pages

Some hardware/operating system architectures support memory pages greater than the default (usually 4KB). The actual implementation of this support depends on the underlying hardware and OS. Applications that perform a lot of memory accesses may obtain performance improvements by using large pages due to reduced Translation Lookaside Buffer (TLB) misses.

Currently, MySQL supports only the Linux implementation of large pages support (which is called HugeTLB in Linux). We have plans to extend this support to FreeBSD, Solaris and possibly other platforms.

Before large pages can be used on Linux, it is necessary to configure the HugeTLB memory pool. For reference, consult the hugetlbpage.txt file in the Linux kernel source.

This option is disabled by default. It was added in MySQL 5.0.3.

--log[=file_name], -l [file_name]

Log connections and SQL statements received from clients to this file. See Section 5.12.2, “The General Query Log”. If you omit the filename, MySQL uses host_name.log as the filename.

--log-bin=[base_name]

Enable binary logging. The server logs all statements that change data to the binary log, which is used for backup and replication. See Section 5.12.3, “The Binary Log”.

The option value, if given, is the basename for the log sequence. The server creates binary log files in sequence by adding a numeric suffix to the basename. It is recommended that you specify a basename (see Section A.8.1, “Open Issues in MySQL”, for the reason). Otherwise, MySQL uses host_name-bin as the basename.

--log-bin-index[=file_name]

The index file for binary log filenames. See Section 5.12.3, “The Binary Log”. If you omit the filename, and if you didn't specify one with --log-bin, MySQL uses host_name-bin.index as the filename.

--log-bin-trust-function-creators[={0|1}]

With no argument or an argument of 1, this option sets the log_bin_trust_function_creators system variable to 1. With an argument of 0, this option sets the system variable to 0. log_bin_trust_function_creators affects how MySQL enforces restrictions on stored function creation. See Section 17.4, “Binary Logging of Stored Routines and Triggers”.

This option was added in MySQL 5.0.16.

--log-bin-trust-routine-creators[={0|1}]

This is the old name for --log-bin-trust-function-creators. Before MySQL 5.0.16, it also applies to stored procedures, not just stored functions and sets the log_bin_trust_routine_creators system variable. As of 5.0.16, this option is deprecated. It is recognized for backward compatibility but its use results in a warning.

This option was added in MySQL 5.0.6.

--log-error[=file_name]

Log errors and startup messages to this file. See Section 5.12.1, “The Error Log”. If you omit the filename, MySQL uses host_name.err. If the filename has no extension, the server adds an extension of .err.

--log-isam[=file_name]

Log all MyISAM changes to this file (used only when debugging MyISAM).

--log-long-format (DEPRECATED)

Log extra information to the update log, binary update log, and slow query log, if they have been activated. For example, the username and timestamp are logged for all queries. This option is deprecated, as it now represents the default logging behavior. (See the description for --log-short-format.) The --log-queries-not-using-indexes option is available for the purpose of logging queries that do not use indexes to the slow query log.

--log-queries-not-using-indexes

If you are using this option with --log-slow-queries, queries that do not use indexes are logged to the slow query log. See Section 5.12.4, “The Slow Query Log”.

--log-short-format

Log less information to the update log, binary update log, and slow query log, if they have been activated. For example, the username and timestamp are not logged for queries.

--log-slow-admin-statements

Log slow administrative statements such as OPTIMIZE TABLE, ANALYZE TABLE, and ALTER TABLE to the slow query log.

--log-slow-queries[=file_name]

Log all queries that have taken more than long_query_time seconds to execute to this file. See Section 5.12.4, “The Slow Query Log”. See the descriptions of the --log-long-format and --log-short-format options for details.

--log-warnings=[level], -W [level]

Print out warnings such as Aborted connection... to the error log. Enabling this option is recommended, for example, if you use replication (you get more information about what is happening, such as messages about network failures and reconnections). This option is enabled (1) by default, and the default level value if omitted is 1. To disable this option, use --log-warnings=0. Aborted connections are not logged to the error log unless the value is greater than 1. See Section A.2.10, “Communication Errors and Aborted Connections”.

--low-priority-updates

Give table-modifying operations (INSERT, REPLACE, DELETE, UPDATE) lower priority than selects. This can also be done via {INSERT | REPLACE | DELETE | UPDATE} 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. See Section 5.7.5, “How to Run MySQL as a Normal User”.

--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, separate them by commas. You can also use a value of "" to disable this option. If this option is used, each time mysqld opens a MyISAM table, it checks whether the table is marked as crashed or wasn't closed properly. (The last option works only if you are running with external locking disabled.) If this is the case, mysqld runs a check on the table. If the table was corrupted, mysqld attempts to repair it.

The following options affect how the repair works:

Before the server automatically repairs a table, it writes a note about the repair to 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 forces a repair of a table even if some rows would be deleted, but it keeps the old data file as a backup so that you can later examine what happened.

See Section 14.1.1, “MyISAM Startup Options”.

--ndb-connectstring=connect_string

When using the NDB storage engine, it is possible to point out the management server that distributes the cluster configuration by setting the connect string option. See Section 15.4.4.2, “The MySQL Cluster connectstring”, for syntax.

--ndbcluster

If the binary includes support for the NDB Cluster storage engine, this option enables the engine, which is disabled by default. See Chapter 15, MySQL Cluster.

--old-passwords

Force the server to generate short (pre-4.1) password hashes for new passwords. This is useful for compatibility when the server must support older client programs. See Section 5.8.9, “Password Hashing as of MySQL 4.1”.

--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 E.1, “Debugging a MySQL Server”.

--open-files-limit=count

Change the number of file descriptors available to mysqld. If this option is not set or is set to 0, mysqld uses the value to reserve file descriptors with setrlimit(). If the value is 0, mysqld reserves max_connections×5 or max_connections + table_open_cache×2 files (whichever is larger). You should try increasing this value if mysqld gives you the error Too many open files.

--pid-file=path

The pathname of the process ID file. This file is used by other programs such as mysqld_safe to determine the server's process ID.

--port=port_num, -P port_num

The port number to use when listening for TCP/IP connections. The port number must be 1024 or higher unless the server is started by the root system user.

--port-open-timeout=num

On some systems, when the server is stopped, the TCP/IP port might not become available immediately. If the server is restarted quickly afterward, its attempt to reopen the port can fail. This option indicates how many seconds the server should wait for the TCP/IP port to become free if it cannot be opened. The default is not to wait. This option was added in MySQL 5.0.19.

--safe-mode

Skip some optimization stages.

--safe-show-database (DEPRECATED)

See Section 5.8.3, “Privileges Provided by MySQL”.

--safe-user-create

If this option is enabled, a user cannot create new MySQL users by using the GRANT statement, if the user doesn't have the INSERT privilege for the mysql.user table or any column in the table.

--secure-auth

Disallow authentication by clients that attempt to use accounts that have old (pre-4.1) passwords.

--shared-memory

Enable shared-memory connections by local clients. This option is available only on Windows.

--shared-memory-base-name=name

The name of shared memory to use for shared-memory connections. This option is available only on Windows. The default name is MYSQL. The name is case sensitive.

--skip-bdb

Disable the BDB storage engine. This saves memory and might speed up some operations. Do not use this option 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 to be used only if you think you have found a bug in this feature.)

--skip-external-locking

Do not use external locking (system locking). With external locking disabled, you must shut down the server to use myisamchk. (See Section 1.4.3, “MySQL Stability”.) To avoid this requirement, use the CHECK TABLE and REPAIR TABLE statements to check and repair MyISAM tables.

External locking has been disabled by default since MySQL 4.0.

--skip-grant-tables

This option causes the server not to use the privilege system at all, which gives anyone with access to the server unrestricted access to all databases. You can cause a running server to start using the grant tables again by executing mysqladmin flush-privileges or mysqladmin reload command from a system shell, or by issuing a MySQL FLUSH PRIVILEGES statement after connecting to the server. This option also suppresses loading of user-defined functions (UDFs).

--skip-host-cache

Do not use the internal hostname cache for faster name-to-IP resolution. Instead, query the DNS server every time a client connects. See Section 7.5.6, “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 option if you require InnoDB tables.

--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 7.5.6, “How MySQL Uses DNS”.

--skip-ndbcluster

Disable the NDB Cluster storage engine. This is the default for binaries that were built with NDB Cluster storage engine support; the server allocates memory and other resources for this storage engine only if the --ndbcluster option is given explicitly. See Section 15.4.3, “Quick Test Setup of MySQL Cluster”, for an example of usage.

--skip-networking

Don't listen for TCP/IP connections at all. All interaction with mysqld must be made via named pipes or shared memory (on Windows) or Unix socket files (on Unix). This option is highly recommended for systems where only local clients are allowed. See Section 7.5.6, “How MySQL Uses DNS”.

--standalone

Available on Windows NT-based systems only; instructs the MySQL server not to run as a service.

--symbolic-links, --skip-symbolic-links

Enable or disable symbolic link support. This option has different effects on Windows and Unix:

--skip-safemalloc

If MySQL is configured with --with-debug=full, all MySQL programs check 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

With this option, the SHOW DATABASES statement is allowed only to users who have the SHOW DATABASES privilege, and the statement displays all database names. Without this option, SHOW DATABASES is allowed to all users, but displays each database name only if the user has the SHOW DATABASES privilege or some privilege for the database. Note that any global privilege is considered a privilege for the database.

--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 E.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 when listening for local connections. The default value is /tmp/mysql.sock. On Windows, the option specifies the pipe name to use when listening for local connections that use a named pipe. The default value is MySQL (not case sensitive).

--sql-mode=value[,value[,value...]]

Set the SQL mode. See Section 5.2.5, “The Server SQL Mode”.

--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, because it is being allocated to the directory entry cache rather than to the disk cache.

--transaction-isolation=level

Sets the default transaction isolation level. The level value can be READ-UNCOMMITTED, READ-COMMITTED, REPEATABLE-READ, or SERIALIZABLE. See Section 13.4.6, “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. 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. For more information about the storage location of temporary files, see Section A.4.4, “Where MySQL Stores Temporary Files”. 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 fails.

--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 changes its user ID during its startup sequence, causing it to run as that particular user rather than as root. See Section 5.7.1, “General Security Guidelines”.

To avoid a possible security hole where a user adds a --user=root option to a 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 $MYSQL_HOME/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 is 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.

To see the values that a server will use based on its compiled-in defaults and any option files that it reads, use this command:

mysqld --verbose --help

To see the values that a server will use based on its compiled-in defaults, ignoring the settings in any option files, use this command:

mysqld --no-defaults --verbose --help

To see the current values used by a running server, use the SHOW VARIABLES statement.

Section 5.2.3, “Using System Variables”, discusses the syntax for setting and displaying system variable values.

Section 5.2.3.2, “Dynamic System Variables”, lists the variables that can be set at runtime.

Information on tuning sytem variables can be found in Section 7.5.2, “Tuning Server Parameters”.

Section 14.2.4, “InnoDB Startup Options and System Variables”, lists InnoDB system variables.

auto_increment_increment

auto_increment_increment and auto_increment_offset are intended for use with master-to-master replication, and can be used to control the operation of AUTO_INCREMENT columns. Both variables can be set globally or locally, and each can assume an integer value between 1 and 65,535 inclusive. Setting the value of either of these two variables to 0 causes its value to be set to 1 instead. Attempting to set the value of either of these two variables to an integer greater than 65,535 or less than 0 causes its value to be set to 65,535 instead. Attempting to set the value of auto_increment_increment or auto_increment_offset to a non-integer value gives rise to an error, and the actual value of the variable remains unchanged.

These two variables effect AUTO_INCREMENT column behavior as follows:

Should one or both of these variables be changed and then new rows inserted into a table containing an AUTO_INCREMENT column, the results may seem counterintuitive because the series of AUTO_INCREMENT values is calculated without regard to any values already present in the column, and the next value inserted is the least value in the series that is greater than the maximum existing value in the AUTO_INCREMENT column. In other words, the series is calculated like so:

auto_increment_offset + N × auto_increment_increment

where N is a positive integer value in the series [1, 2, 3, ...]. For example:

mysql> SHOW VARIABLES LIKE 'auto_inc%';
+--------------------------+-------+
| Variable_name            | Value |
+--------------------------+-------+
| auto_increment_increment | 10    |
| auto_increment_offset    | 5     |
+--------------------------+-------+
2 rows in set (0.00 sec)

mysql> SELECT col FROM autoinc1;
+-----+
| col |
+-----+
|   1 |
|  11 |
|  21 |
|  31 |
+-----+
4 rows in set (0.00 sec)

mysql> INSERT INTO autoinc1 VALUES (NULL), (NULL), (NULL), (NULL);
Query OK, 4 rows affected (0.00 sec)
Records: 4  Duplicates: 0  Warnings: 0

mysql> SELECT col FROM autoinc1;
+-----+
| col |
+-----+
|   1 |
|  11 |
|  21 |
|  31 |
|  35 |
|  45 |
|  55 |
|  65 |
+-----+
8 rows in set (0.00 sec)

The values shown for auto_increment_increment and auto_increment_offset generate the series 5 + N × 10, that is, [5, 15, 25, 35, 45, ...]. The greatest value present in the col column prior to the INSERT is 31, and the next available value in the AUTO_INCREMENT series is 35, so the inserted values for col begin at that point and the results are as shown for the SELECT query.

It is important to remember that it is not possible to confine the effects of these two variables to a single table, and thus they do not take the place of the sequences offered by some other database management systems; these variables control the behavior of all AUTO_INCREMENT columns in all tables on the MySQL server. If one of these variables is set globally, its effects persist until the global value is changed or overridden by setting them locally, or until mysqld is restarted. If set locally, the new value affects AUTO_INCREMENT columns for all tables into which new rows are inserted by the current user for the duration of the session, unless the values are changed during that session.

The auto_increment_increment variable was added in MySQL 5.0.2. Its default value is 1. See Section 6.13, “Auto-Increment in Multiple-Master Replication”.

auto_increment_offset

This variable was introduced in MySQL 5.0.2. Its default value is 1. For particulars, see the description for auto_increment_increment.

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() system call should have more details. Check your OS documentation for the maximum value for this variable. back_log cannot be set higher than your operating system limit.

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 allocate memory for this cache.

bdb_home

The base directory for BDB tables. This should be assigned the same value as the datadir variable.

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 allocate memory for this cache.

bdb_logdir

The directory where the BDB storage engine writes its log files. This variable can be set with the --bdb-logdir option.

bdb_max_lock

The maximum number of locks that can be active for a BDB table (10,000 by default). You should increase this value 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 ...

bdb_shared_data

This is ON if you are using --bdb-shared-data to start Berkeley DB in multi-process mode. (Do not use DB_PRIVATE when initializing Berkeley DB.)

bdb_tmpdir

The BDB temporary file directory.

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 if the server has the binary log enabled (--log-bin option). If you often use large, multiple-statement transactions, you can increase this cache size 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. See Section 5.12.3, “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 when adding data to non-empty tables. This variable limits the size of the cache tree in bytes per thread. Setting it to 0 disables this optimization. The default value is 8MB.

character_set_client

The character set for statements that arrive from the client.

character_set_connection

The character set used for literals that do not have a character set introducer and for number-to-string conversion.

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.

character_set_filesystem

The filesystem character set. This variable is used to interpret string literals that refer to filenames, such as in the LOAD DATA INFILE and SELECT ... INTO OUTFILE statements and the LOAD_FILE() function. Such filenames are converted from character_set_client to character_set_filesystem before the file opening attempt occurs. The default value is binary, which means that no conversion occurs. For systems on which multi-byte filenames are allowed, a different value may be more appropriate. For example, if the system represents filenames using UTF-8, set character_set_filesytem to 'utf8'. This variable was added in MySQL 5.0.19.

character_set_results

The character set used for returning query results to the client.

character_set_server

The server's default character set.

character_set_system

The character set used by the server for storing identifiers. The value is always utf8.

character_sets_dir

The directory where character sets are installed.

collation_connection

The collation of the connection character set.

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.

collation_server

The server's default collation.

completion_type