5.1.2. Server Command Options

When you start the mysqld server, you can specify program options using any of the methods described in Section 4.2.3, “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 that 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 4.2.3.3, “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 options. For a brief summary, execute mysqld --help. To see the full list, use mysqld --verbose --help.

The following list shows some of the most common server options. Additional options are described in other sections:

You can also set the values of server system variables by using variable names as options, as described at the end of this section.

Some options control the size of buffers or caches. For a given buffer, the server might need to allocate internal data structures. These structures typically are allocated from the total memory allocated to the buffer, and the amount of space required might be platform dependent. This means that when you assign a value to an option that controls a buffer size, the amount of space actually available might differ from the value assigned. In some cases, the amount might be less than the value assigned. It is also possible that the server will adjust a value upward. For example, if you assign a value of 0 to an option for which the minimal value is 1024, the server will set the value to 1024.

Values for buffer sizes, lengths, and stack sizes are given in bytes unless otherwise specified.

Some options take file name values. Unless otherwise specified, the default file location is the data directory if the value is a relative path name. To specify the location explicitly, use an absolute path name. Suppose that the data directory is /var/mysql/data. If a file-valued option is given as a relative path name, it will be located under /var/mysql/data. If the value is an absolute path name, its location is as given by the path name.

  • --help, -?

    Command-Line Format-?
    --help
    Option-File Formathelp

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

  • --allow-suspicious-udfs

    Command-Line Format--allow-suspicious-udfs
    Option-File Formatallow-suspicious-udfs
     Permitted Values
    Typeboolean
    DefaultFALSE

    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. See Section 23.3.2.6, “User-Defined Function Security Precautions”.

  • --ansi

    Command-Line Format--ansi
    -a
    Option-File Formatansi

    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 1.8.3, “Running MySQL in ANSI Mode”, and Section 5.1.7, “Server SQL Modes”.

  • --basedir=path, -b path

    Command-Line Format--basedir=path
    -b
    Option-File Formatbasedir
    Option Sets VariableYes, basedir
    Variable Namebasedir
    Variable ScopeGlobal
    Dynamic VariableNo
     Permitted Values
    Typefile name

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

  • --big-tables

    Command-Line Format--big-tables
    Option-File Formatbig-tables
    Option Sets VariableYes, big_tables
    Variable Namebig-tables
    Variable ScopeGlobal, Session
    Dynamic VariableYes
     Permitted Values
    Typeboolean

    Enable large result sets by saving all temporary sets in files. This option prevents most “table full” errors, but also slows down queries for which in-memory tables would suffice. Since MySQL 3.23.2, the server 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

    Command-Line Format--bind-address=name
    Option-File Formatbind-address=name
    Variable Namebind-address
    Variable ScopeGlobal
    Dynamic VariableNo
     Permitted Values
    Typestring
    Default0.0.0.0
    Range0.0.0.0-255.255.255.255

    The IP address to bind to. Only one address can be selected. If this option is specified multiple times, the last address given is used.

    If no address or 0.0.0.0 is specified, the server listens on all interfaces.

  • --binlog-format={ROW|STATEMENT|MIXED}

    Command-Line Format--binlog-format=format
    Option-File Formatbinlog-format=format
    Option Sets VariableYes, binlog_format
    Variable Namebinlog_format
    Variable ScopeGlobal, Session
    Dynamic VariableYes
     Permitted Values
    Typeenumeration
    DefaultSTATEMENT
    Valid ValuesROW, STATEMENT, MIXED

    Specify whether to use row-based, statement-based, or mixed replication. Statement-based is the default in MySQL 5.5. See Section 17.1.2, “Replication Formats”.

    Previous to MySQL 5.5, setting the binary logging format without enabling binary logging prevented the MySQL server from starting. In MySQL 5.5, the server starts in such cases, the binlog_format global system variable is set, and a warning is logged instead of an error. (Bug#42928)

  • --bootstrap

    Command-Line Format--bootstrap
    Option-File Formatbootstrap

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

    This option is unavailable if MySQL was configured with the DISABLE_GRANT_OPTIONS compiler flag. See Section 2.11.4, “MySQL Source-Configuration Options”.

  • --character-sets-dir=path

    Command-Line Format--character-sets-dir=path
    Option-File Formatcharacter-sets-dir=path
    Option Sets VariableYes, character_sets_dir
    Variable Namecharacter-sets-dir
    Variable ScopeGlobal
    Dynamic VariableNo
     Permitted Values
    Typedirectory name

    The directory where character sets are installed. See Section 9.5, “Character Set Configuration”.

  • --character-set-client-handshake

    Command-Line Format--character-set-client-handshake
    Option-File Formatcharacter-set-client-handshake
     Permitted Values
    Typeboolean
    DefaultTRUE

    Do not 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

    Command-Line Format--character-set-filesystem=name
    Option-File Formatcharacter-set-filesystem
    Option Sets VariableYes, character_set_filesystem
    Variable Namecharacter_set_filesystem
    Variable ScopeGlobal, Session
    Dynamic VariableYes
     Permitted Values
    Typestring

    The file system character set. This option sets the character_set_filesystem system variable.

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

    Command-Line Format--character-set-server
    Option-File Formatcharacter-set-server
    Option Sets VariableYes, character_set_server
    Variable Namecharacter_set_server
    Variable ScopeGlobal, Session
    Dynamic VariableYes
     Permitted Values
    Typestring

    Use charset_name as the default server character set. See Section 9.5, “Character Set Configuration”. If you use this option to specify a nondefault character set, you should also use --collation-server to specify the collation.

  • --chroot=path, -r path

    Command-Line Format--chroot=name
    -r name
    Option-File Formatchroot
     Permitted Values
    Typefile name

    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

    Command-Line Format--collation-server
    Option-File Formatcollation-server
    Option Sets VariableYes, collation_server
    Variable Namecollation_server
    Variable ScopeGlobal, Session
    Dynamic VariableYes
     Permitted Values
    Typestring

    Use collation_name as the default server collation. See Section 9.5, “Character Set Configuration”.

  • --console

    Command-Line Format--console
    Option-File Formatconsole
    Platform Specificwindows

    (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

    Command-Line Format--core-file
    Option-File Formatcore-file
     Permitted Values
    Typeboolean
    DefaultFALSE

    Write a core file if mysqld dies. The name and location of the core file is system dependent. On Linux, a core file named core.pid is written to the current working directory of the process, which for mysqld is the data directory. pid represents the process ID of the server process. On Mac OS X, a core file named core.pid is written to the /cores directory. On Solaris, use the coreadm command to specify where to write the core file and how to name it.

    For some systems, to get a core file you must also specify the --core-file-size option to mysqld_safe. See Section 4.3.2, “mysqld_safe — MySQL Server Startup Script”. On some systems, such as Solaris, you do not get a core file if you are also using the --user option. There might be additional restrictions or limitations. For example, it might be necessary to execute ulimit -c unlimited before starting the server. Consult your system documentation.

  • --datadir=path, -h path

    Command-Line Format--datadir=path
    -h
    Option-File Formatdatadir
    Option Sets VariableYes, datadir
    Variable Namedatadir
    Variable ScopeGlobal
    Dynamic VariableNo
     Permitted Values
    Typefile name

    The path to the data directory.

  • --debug[=debug_options], -# [debug_options]

    Command-Line Format--debug[=debug_options]
    Option-File Formatdebug
    Variable Namedebug
    Variable ScopeGlobal, Session
    Dynamic VariableYes
     Permitted Values
    Typestring
    Default'd:t:o,/tmp/mysqld.trace'

    If MySQL is configured with -DWITH_DEBUG=1, you can use this option to get a trace file of what mysqld is doing. A typical debug_options string is 'd:t:o,file_name'. The default is 'd:t:i:o,mysqld.trace'. See MySQL Internals: Porting.

    Using -DWITH_DEBUG=1 to configure MySQL with debugging support enables you to use the --debug="d,parser_debug" option when you start the server. This causes the Bison parser that is used to process SQL statements to dump a parser trace to the server's standard error output. Typically, this output is written to the error log.

    This option may be given multiple times. Values that begin with + or - are added to or subtracted from the previous value. For example, --debug=T --debug=+P sets the value to P:T.

  • --debug-sync-timeout[=N]

    Command-Line Format--debug-sync-timeout[=#]
    Option-File Formatdebug-sync-timeout
     Permitted Values
    Typenumeric

    Controls whether the Debug Sync facility for testing and debugging is enabled. Use of Debug Sync requires that MySQL be configured with the -DENABLE_DEBUG_SYNC=1 option (see Section 2.11.4, “MySQL Source-Configuration Options”). If Debug Sync is not compiled in, this option is not available. The option value is a timeout in seconds. The default value is 0, which disables Debug Sync. To enable it, specify a value greater than 0; this value also becomes the default timeout for individual synchronization points. If the option is given without a value, the timeout is set to 300 seconds.

    For a description of the Debug Sync facility and how to use synchronization points, see MySQL Internals: Test Synchronization.

  • --default-character-set=charset_name

    Command-Line Format--default-character-set=name
    -C name
    Option-File Formatdefault-character-set=name
    Deprecated5.0
     Permitted Values
    Typestring

    Use charset_name as the default character set. This option is deprecated in favor of --character-set-server. See Section 9.5, “Character Set Configuration”. --default-character-set was removed in MySQL 5.5.3.

  • --default-collation=collation_name

    Command-Line Format--default-collation=name
    Option-File Formatdefault-collation=name
    Deprecated4.1.3
     Permitted Values
    Typestring

    Use collation_name as the default collation. This option is deprecated in favor of --collation-server. See Section 9.5, “Character Set Configuration”. --default-collation was removed in MySQL 5.5.3.

  • --default-storage-engine=type

    Command-Line Format--default-storage-engine=name
    Option-File Formatdefault-storage-engine
    Option Sets VariableYes, default_storage_engine
    Variable Namedefault-storage-engine
    Variable ScopeGlobal, Session
    Dynamic VariableYes
     Permitted Values (<= 5.5.4)
    Typeenumeration
    DefaultMyISAM
     Permitted Values (>= 5.5.5)
    Typeenumeration
    DefaultInnoDB

    Set the default storage engine (table type) for tables. See Chapter 13, Storage Engines.

  • --default-time-zone=timezone

    Command-Line Format--default-time-zone=name
    Option-File Formatdefault-time-zone
     Permitted Values
    Typestring

    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}]

    Command-Line Format--delay-key-write[=name]
    Option-File Formatdelay-key-write
    Option Sets VariableYes, delay_key_write
    Variable Namedelay-key-write
    Variable ScopeGlobal
    Dynamic VariableYes
     Permitted Values
    Typeenumeration
    DefaultON
    Valid ValuesON, OFF, 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 7.11.2, “Tuning Server Parameters”, and Section 13.5.1, “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

    Command-Line Format--des-key-file=file_name
    Option-File Formatdes-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

    Command-Line Format--enable-named-pipe
    Option-File Formatenable-named-pipe
    Option Sets VariableYes, named_pipe
    Platform Specificwindows

    Enable support for named pipes. This option applies only on Windows.

  • --enable-pstack

    Version Removed5.5.7
    Command-Line Format--enable-pstack
    Option-File Formatenable-pstack
    Deprecated5.1.54
     Permitted Values
    Typeboolean
    DefaultFALSE

    This option is nonfunctional before MySQL 5.5.7 and removed in 5.5.7.

  • --engine-condition-pushdown={ON|OFF}

    Version Deprecated5.5.3
    Command-Line Format--engine-condition-pushdown
    Option-File Formatengine-condition-pushdown
    Option Sets VariableYes, engine_condition_pushdown
    Variable Nameengine_condition_pushdown
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Deprecated5.5.3, by optimizer_switch
     Permitted Values
    Typeboolean
    DefaultON

    Sets the engine_condition_pushdown system variable. For more information, see Section 7.13.3, “Engine Condition Pushdown Optimization”.

  • --event-scheduler[=value]

    Command-Line Format--event-scheduler[=value]
    Option-File Formatevent-scheduler
    Option Sets VariableYes, event_scheduler
    Variable Nameevent_scheduler
    Variable ScopeGlobal
    Dynamic VariableYes
     Permitted Values
    Typeenumeration
    DefaultOFF
    Valid ValuesON, OFF, DISABLED

    Enable or disable, and start or stop, the event scheduler.

    For detailed information, see The --event-scheduler Option.

  • --exit-info[=flags], -T [flags]

    Command-Line Format--exit-info[=flags]
    -T [flags]
    Option-File Formatexit-info
     Permitted Values
    Typenumeric

    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

    Command-Line Format--external-locking
    Option-File Formatexternal-locking
    Option Sets VariableYes, skip_external_locking
    Disabled byskip-external-locking
     Permitted Values
    Typeboolean
    DefaultFALSE

    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.

    For more information about external locking, including conditions under which it can and cannot be used, see Section 7.10.5, “External Locking”.

  • --flush

    Command-Line Format--flush
    Option-File Formatflush
    Variable Nameflush
    Variable ScopeGlobal
    Dynamic VariableYes
     Permitted Values
    Typeboolean
    DefaultOFF

    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 C.5.4.2, “What to Do If MySQL Keeps Crashing”.

  • --gdb

    Command-Line Format--gdb
    Option-File Formatgdb
     Permitted Values
    Typeboolean
    DefaultFALSE

    Install an interrupt handler for SIGINT (needed to stop mysqld with ^C to set breakpoints) and disable stack tracing and core file handling. See MySQL Internals: Porting.

  • --general-log[={0|1}]

    Command-Line Format--general-log
    Option-File Formatgeneral-log
    Option Sets VariableYes, general_log
    Variable Namegeneral_log
    Variable ScopeGlobal
    Dynamic VariableYes
     Permitted Values
    Typeboolean
    DefaultOFF

    Specify the initial general query log state. With no argument or an argument of 1, the --general-log option enables the log. If omitted or given with an argument of 0, the option disables the log.

  • --init-file=file_name

    Command-Line Format--init-file=file_name
    Option-File Formatinit-file=file_name
    Option Sets VariableYes, init_file
    Variable Nameinit_file
    Variable ScopeGlobal
    Dynamic VariableNo
     Permitted Values
    Typefile name

    Read SQL statements from this file at startup. Each statement must be on a single line and should not include comments.

    This option is unavailable if MySQL was configured with the DISABLE_GRANT_OPTIONS compiler flag. See Section 2.11.4, “MySQL Source-Configuration Options”.

  • --innodb-xxx

    The InnoDB options are listed in Section 13.6.4, “InnoDB Startup Options and System Variables”.

  • --language=lang_name, -L lang_name

    Version Deprecated5.5.0
    Command-Line Format--language=name
    -L
    Option-File Formatlanguage
    Option Sets VariableYes, language
    Variable Namelanguage
    Variable ScopeGlobal
    Dynamic VariableNo
    Deprecated5.5.0, by lc-messages-dir
     Permitted Values
    Typedirectory name
    Default/usr/local/mysql/share/mysql/english/

    The language to use for error messages. lang_name can be given as the language name or as the full path name to the directory where the language files are installed. See Section 9.2, “Setting the Error Message Language”.

    As of MySQL 5.5, --lc-messages-dir and --lc-messages should be used rather than --language, which is deprecated and handled as an alias for --lc-messages-dir.

  • --large-pages

    Command-Line Format--large-pages
    Option-File Formatlarge-pages
    Option Sets VariableYes, large_pages
    Variable Namelarge_pages
    Variable ScopeGlobal
    Dynamic VariableNo
    Platform Specificlinux
     Permitted Values
    Type (linux)boolean
    DefaultFALSE

    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 operating system. Applications that perform a lot of memory accesses may obtain performance improvements by using large pages due to reduced Translation Lookaside Buffer (TLB) misses.

    MySQL 5.5 supports the Linux implementation of large page support (which is called HugeTLB in Linux). See Section 7.11.4.2, “Enabling Large Page Support”. For Solaris support of large pages, see the description of the --super-large-pages option.

    --large-pages is disabled by default.

  • --lc-messages=locale_name

    Command-Line Format--lc-messages=name
    Option-File Formatlc-messages
    Option Sets VariableYes, lc_messages
    Variable Namelc-messages
    Variable ScopeGlobal, Session
    Dynamic VariableYes
     Permitted Values
    Typestring

    The locale to use for error messages. The server converts the argument to a language name and combines it with the value of the --lc-messages-dir to produce the location for the error message file. See Section 9.2, “Setting the Error Message Language”.

  • --lc-messages-dir=path

    Command-Line Format--lc-messages-dir=path
    Option-File Formatlc-messages-dir
    Option Sets VariableYes, lc_messages_dir
    Variable Namelc-messages-dir
    Variable ScopeGlobal
    Dynamic VariableNo
     Permitted Values
    Typedirectory name

    The directory where error messages are located. The value is used together with the value of --lc-messages to produce the location for the error message file. See Section 9.2, “Setting the Error Message Language”.

  • --log[=file_name], -l [file_name]

    Command-Line Format--log[=name]
    -l
    Option-File Formatlog
    Option Sets VariableYes, log
    Variable Namelog
    Variable ScopeGlobal
    Dynamic VariableYes
    Deprecated5.1.29, by general-log
     Permitted Values
    Typestring
    DefaultOFF

    This option enables logging to the general query log, which contains entries that record client connections and SQL statements received from clients. The log output destination can be selected with the --log-output option. If you omit the file name, MySQL uses host_name.log as the file name. See Section 5.2.1, “Selecting General Query and Slow Query Log Output Destinations”, and Section 5.2.3, “The General Query Log”.

    The --log option is deprecated and will be removed (along with the log system variable) in MySQL 7.0. Instead, use the --general_log option to enable the general query log and the --general_log_file=file_name option to set the general query log file name.

  • --log-error[=file_name]

    Command-Line Format--log-error[=name]
    Option-File Formatlog-error
    Option Sets VariableYes, log_error
    Variable Namelog_error
    Variable ScopeGlobal
    Dynamic VariableNo
     Permitted Values
    Typefile name

    Log errors and startup messages to this file. See Section 5.2.2, “The Error Log”. If you omit the file name, MySQL uses host_name.err. If the file name has no extension, the server adds an extension of .err.

  • --log-isam[=file_name]

    Command-Line Format--log-isam[=name]
    Option-File Formatlog-isam
     Permitted Values
    Typefile name

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

  • --log-long-format

    Command-Line Format--log-long-format
    -0
    Option-File Formatlog-long-format
    Deprecated4.1

    Log extra information to the binary log and slow query log, if they have been activated. For example, the user name 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-long-format was removed in MySQL 5.5.3.

  • --log-output[=value,...]

    Command-Line Format--log-output[=name]
    Option-File Formatlog-output
    Option Sets VariableYes, log_output
    Variable Namelog_output
    Variable ScopeGlobal
    Dynamic VariableYes
     Permitted Values
    Typeset
    DefaultFILE
    Valid ValuesTABLE, FILE, NONE

    This option determines the destination for general query log and slow query log output. The option value can be given as one or more of the words TABLE, FILE, or NONE. If the option is given without a value, the default is FILE. TABLE select logging to the general_log and slow_log tables in the mysql database as a destination. FILE selects logging to log files as a destination. NONE disables logging. If NONE is present in the option value, it takes precedence over any other words that are present. TABLE and FILE can both be given to select to both log output destinations.

    This option selects log output destinations, but does not enable log output. To do that, use the --general_log and --slow_query_log options. For FILE logging, the --general_log_file and -slow_query_log_file options determine the log file location. For more information, see Section 5.2.1, “Selecting General Query and Slow Query Log Output Destinations”.

  • --log-queries-not-using-indexes

    Command-Line Format--log-queries-not-using-indexes
    Option-File Formatlog-queries-not-using-indexes
    Option Sets VariableYes, log_queries_not_using_indexes
    Variable Namelog_queries_not_using_indexes
    Variable ScopeGlobal
    Dynamic VariableYes
     Permitted Values
    Typeboolean

    If you are using this option with the slow query log enabled, queries that are expected to retrieve all rows are logged. See Section 5.2.5, “The Slow Query Log”. This option does not necessarily mean that no index is used. For example, a query that uses a full index scan uses an index but would be logged because the index would not limit the number of rows.

  • --log-short-format

    Command-Line Format--log-short-format
    Option-File Formatlog-short-format
     Permitted Values
    Typeboolean
    DefaultFALSE

    Originally intended to log less information to the binary log and slow query log, if they have been activated. However, this option is not operational.

  • --log-slow-admin-statements

    Command-Line Format--log-slow-admin-statements
    Option-File Formatlog-slow-admin-statements
     Permitted Values
    Typeboolean
    DefaultFALSE

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

  • --log-slow-queries[=file_name]

    Command-Line Format--log-slow-queries[=name]
    Option-File Formatlog-slow-queries
    Option Sets VariableYes, log_slow_queries
    Variable Namelog_slow_queries
    Variable ScopeGlobal
    Dynamic VariableYes
    Deprecated5.1.29, by slow-query-log
     Permitted Values
    Typeboolean

    This option enables logging to the slow query log, which contains entries for all queries that have taken more than long_query_time seconds to execute. See the descriptions of the --log-long-format and --log-short-format options for details. The log output destination can be selected with the --log-output option. If you omit the file name, MySQL uses host_name-slow.log as the file name. See Section 5.2.1, “Selecting General Query and Slow Query Log Output Destinations”, and Section 5.2.5, “The Slow Query Log”.

    The --log-slow-queries option is deprecated and will be removed (along with the log_slow_queries system variable) in MySQL 7.0. Instead, use the --slow_query_log option to enable the slow query log and the --slow_query_log_file=file_name option to set the slow query log file name.

  • --log-tc=file_name

    Command-Line Format--log-tc=name
    Option-File Formatlog-tc
     Permitted Values
    Typefile name
    Defaulttc.log

    The name of the memory-mapped transaction coordinator log file (for XA transactions that affect multiple storage engines when the binary log is disabled). The default name is tc.log. The file is created under the data directory if not given as a full path name. Currently, this option is unused.

  • --log-tc-size=size

    Command-Line Format--log-tc-size=#
    Option-File Formatlog-tc-size
     Permitted Values
    Platform Bit Size32
    Typenumeric
    Default24576
    Max Value4294967295
     Permitted Values
    Platform Bit Size64
    Typenumeric
    Default24576
    Max Value18446744073709547520

    The size in bytes of the memory-mapped transaction coordinator log. The default size is 24KB.

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

    Command-Line Format--log-warnings[=#]
    -W [#]
    Option-File Formatlog-warnings
    Option Sets VariableYes, log_warnings
    Variable Namelog_warnings
    Variable ScopeGlobal, Session
    Dynamic VariableYes
    Disabled byskip-log-warnings
     Permitted Values
    Platform Bit Size64
    Typenumeric
    Default1
    Range0-18446744073709547520

    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. If the value is greater than 1, aborted connections are written to the error log, and access-denied errors for new connection attempts are written. See Section C.5.2.11, “Communication Errors and Aborted Connections”.

    If a slave server was started with --log-warnings enabled, the slave prints messages to the error log to provide information about its status, such as the binary log and relay log coordinates where it starts its job, when it is switching to another relay log, when it reconnects after a disconnect, and so forth. The server logs messages about statements that are unsafe for statement-based logging only if --log-warnings is enabled.

  • --low-priority-updates

    Command-Line Format--low-priority-updates
    Option-File Formatlow-priority-updates
    Option Sets VariableYes, low_priority_updates
    Variable Namelow_priority_updates
    Variable ScopeGlobal, Session
    Dynamic VariableYes
     Permitted Values
    Typeboolean
    DefaultFALSE

    Give table-modifying operations (INSERT, REPLACE, DELETE, UPDATE) lower priority than selects. This can also be done using {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. This affects only storage engines that use only table-level locking (MyISAM, MEMORY, MERGE). See Section 7.10.2, “Table Locking Issues”.

  • --min-examined-row-limit=number

    Command-Line Format--min-examined-row-limit=#
    Option-File Formatmin-examined-row-limit
    Variable Namemin_examined_row_limit
    Variable ScopeGlobal, Session
    Dynamic VariableYes
     Permitted Values
    Platform Bit Size32
    Typenumeric
    Default0
    Range0-4294967295
     Permitted Values
    Platform Bit Size64
    Typenumeric
    Default0
    Range0-18446744073709547520

    When this option is set, queries which examine fewer than number rows are not written to the slow query log. The default is 0.

  • --memlock

    Command-Line Format--memlock
    Option-File Formatmemlock
    Variable Namelocked_in_memory
    Variable ScopeGlobal
    Dynamic VariableNo
     Permitted Values
    Typeboolean
    DefaultFALSE

    Lock the mysqld process in memory. This option might help if you have a problem where the operating system is causing mysqld to swap to disk.

    --memlock works on systems that support the mlockall() system call; this includes Solaris as well as most Linux distributions that use a 2.4 or newer kernel. On Linux systems, you can tell whether or not mlockall() (and thus this option) is supported by checking to see whether or not it is defined in the system mman.h file, like this:

    shell> grep mlockall /usr/include/sys/mman.h
    

    If mlockall() is supported, you should see in the output of the previous command something like the following:

    extern int mlockall (int __flags) __THROW;
    

    Important

    Using this option requires that you run the server as root, which, for reasons of security, is normally not a good idea. See Section 5.3.6, “How to Run MySQL as a Normal User”.

    You must not try to use this option on a system that does not support the mlockall() system call; if you do so, mysqld will very likely crash as soon as you try to start it.

  • --myisam-block-size=N

    Command-Line Format--myisam-block-size=#
    Option-File Formatmyisam-block-size
     Permitted Values
    Typenumeric
    Default1024
    Range1024-16384

    The block size to be used for MyISAM index pages.

  • --myisam-recover[=option[,option]...]]

    This option is renamed as of MySQL 5.5.3 to --myisam-recover-options. See the description of that option for more information.

  • --myisam-recover-options[=option[,option]...]]

    Version Introduced5.5.3
    Command-Line Format--myisam-recover-options[=name]
    Option-File Formatmyisam-recover-options
    Option Sets VariableYes, myisam_recover_options
     Permitted Values
    Typeenumeration
    DefaultOFF
    Valid ValuesOFF, DEFAULT, BACKUP, FORCE, QUICK

    Set the MyISAM storage engine recovery mode. The option value is any combination of the values of DEFAULT, OFF, BACKUP, FORCE, or QUICK. If you specify multiple values, separate them by commas. Specifying the option with no argument is the same as specifying DEFAULT, and specifying with an explicit value of "" disables recovery (same as not giving the option). If recovery is enabled, each time mysqld opens a MyISAM table, it checks whether the table is marked as crashed or was not 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.

    OptionDescription
    DEFAULTRecovery without backup, forcing, or quick checking.
    OFFRecovery without backup, forcing, or quick checking.
    BACKUPIf the data file was changed during recovery, save a backup of the tbl_name.MYD file as tbl_name-datetime.BAK.
    FORCERun recovery even if we would lose more than one row from the .MYD file.
    QUICKDo not check the rows in the table if there are not any delete blocks.

    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.

    This option was named --myisam-recover, before MySQL 5.5.3. The old option name still works because it is recognized as an unambiguous prefix of the new name, --myisam-recover-options. (Option prefix recognition occurs as described in Section 4.2.3, “Specifying Program Options”.)

    The option value OFF is available as of MySQL 5.5.3.

    See Section 13.5.1, “MyISAM Startup Options”.

  • --old-alter-table

    Command-Line Format--old-alter-table
    Option-File Formatold-alter-table
    Option Sets VariableYes, old_alter_table
    Variable Nameold-alter-table
    Variable ScopeGlobal, Session
    Dynamic VariableYes
     Permitted Values
    Typeboolean
    DefaultOFF

    When this option is given, the server does not use the optimized method of processing an ALTER TABLE operation. It reverts to using a temporary table, copying over the data, and then renaming the temporary table to the original, as used by MySQL 5.0 and earlier. For more information on the operation of ALTER TABLE, see Section 12.1.6, “ALTER TABLE Syntax”.

  • --old-passwords

    Command-Line Format--old_passwords
    Option-File Formatold-passwords
    Option Sets VariableYes, old_passwords
    Variable Nameold_passwords
    Variable ScopeGlobal, Session
    Dynamic VariableYes
     Permitted Values
    Typeboolean
    DefaultFALSE

    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 5.3.2.3, “Password Hashing in MySQL”.

  • --old-style-user-limits

    Command-Line Format--old-style-user-limits
    Option-File Formatold-style-user-limits
     Permitted Values
    Typeboolean
    DefaultFALSE

    Enable old-style user limits. (Before MySQL 5.0.3, account resource limits were counted separately for each host from which a user connected rather than per account row in the user table.) See Section 5.5.4, “Setting Account Resource Limits”.

  • --one-thread

    Command-Line Format--one-thread
    Option-File Formatone-thread

    Only use one thread (for debugging under Linux). This option is available only if the server is built with debugging enabled. See MySQL Internals: Porting.

    This option is deprecated; use --thread_handling=no-threads instead.

  • --open-files-limit=count

    Command-Line Format--open-files-limit=#
    Option-File Formatopen-files-limit
    Option Sets VariableYes, open_files_limit
    Variable Nameopen_files_limit
    Variable ScopeGlobal
    Dynamic VariableNo
     Permitted Values
    Typenumeric
    Default0
    Range0-65535

    Changes the number of file descriptors available to mysqld. You should try increasing the value of this option if mysqld gives you the error Too many open files. mysqld uses the option value to reserve descriptors with setrlimit(). If the requested number of file descriptors cannot be allocated, mysqld writes a warning to the error log.

    mysqld may attempt to allocate more than the requested number of descriptors (if they are available), using the values of max_connections and table_open_cache to estimate whether more descriptors will be needed.

  • --partition[=value]

    Command-Line Format--partition
    Option-File Formatpartition
    Option Sets VariableYes, have_partitioning
    Variable Namepartition
    Variable ScopeGlobal
    Dynamic VariableNo
    Disabled byskip-partition
     Permitted Values
    Typeboolean
    DefaultON

    Enables or disables user-defined partitioning support in the MySQL Server.

  • --pid-file=path

    Command-Line Format--pid-file=file_name
    Option-File Formatpid-file=file_name
    Option Sets VariableYes, pid_file
    Variable Namepid_file
    Variable ScopeGlobal
    Dynamic VariableNo
     Permitted Values
    Typefile name

    The path name of the process ID file. The server creates the file in the data directory unless an absolute path name is given to specify a different directory. This file is used by other programs such as mysqld_safe to determine the server's process ID.

  • --plugin-xxx

    Specifies an option that pertains to a server plugin. For example, many storage engines can be built as plugins, and for such engines, options for them can be specified with a --plugin prefix. Thus, the --innodb_file_per_table option for InnoDB can be specified as --plugin-innodb_file_per_table.

    For boolean options that can be enabled or disabled, the --skip prefix and other alternative formats are supported as well (see Section 4.2.3.2, “Program Option Modifiers”). For example, --skip-plugin-innodb_file_per_table disables innodb_file_per_table.

    The rationale for the --plugin prefix is that it enables plugin options to be specified unambigously if there is a name conflict with a built-in server option. For example, were a plugin writer to name a plugin “sql” and implement a “mode” option, the option name might be --sql-mode, which would conflict with the built-in option of the same name. In such cases, references to the conflicting name are resolved in favor of the built-in option. To avoid the ambiguity, users can specify the plugin option as --plugin-sql-mode. Use of the --plugin prefix for plugin options is recommended to avoid any question of ambiguity.

  • --plugin-load=plugin_list

    Command-Line Format--plugin-load=plugin_list
    Option-File Formatplugin-load
     Permitted Values
    Typestring

    This option tells the server to load the named plugins at startup. The option value is a semicolon-separated list of name=plugin_library pairs. Each name is the name of the plugin, and plugin_library is the name of the shared library that contains the plugin code. Each library file must be located in the directory named by the plugin_dir system variable. For example, if plugins named myplug1 and myplug2 have library files myplug1.so and myplug2.so, use this option to load them at startup:

    shell> mysqld --plugin-load=myplug1=myplug1.so;myplug2=myplug2.so
    

    All plugins to load must be named in the same --plugin-load option. If multiple --plugin-load options are given, only the last one is used.

    Each named plugin is loaded for a single invocation of mysqld only. After a restart, the plugin is not loaded unless --plugin-load is used again. This is in contrast to INSTALL PLUGIN, which adds an entry to the mysql.plugins table to cause the plugin to be loaded for every normal server startup.

    Under normal startup, the server determines which plugins to load by reading the mysql.plugins system table. If the server is started with the --skip-grant-tables option, it does not consult the mysql.plugins table and thus does not load plugins installed with the INSTALL PLUGIN statement. --plugin-load enables plugins to be loaded even when --skip-grant-tables is given. --plugin-load also enables plugins to be loaded at startup under configurations when plugins cannot be loaded at runtime.

    For additional information about plugin loading, see Section 12.4.3.1, “Installing and Uninstalling Plugins”.

  • --port=port_num, -P port_num

    Command-Line Format--port=#
    -P
    Option-File Formatport
    Option Sets VariableYes, port
    Variable Nameport
    Variable ScopeGlobal
    Dynamic VariableNo
     Permitted Values
    Typenumeric
    Default3306

    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

    Command-Line Format--port-open-timeout=#
    Option-File Formatport-open-timeout
     Permitted Values
    Typenumeric
    Default0

    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.

  • --safe-mode

    Command-Line Format--safe-mode
    Option-File Formatsafe-mode
    Deprecated5.0

    Skip some optimization stages.

  • --safe-show-database

    Command-Line Format--safe-show-database(until 4.1.1) 
    Option-File Formatsafe-show-database
    Variable Namesafe_show_database
    Variable ScopeGlobal
    Dynamic VariableYes
    Deprecated4.0.2
     Permitted Values
    Typeboolean

    This option is deprecated and does not do anything because there is a SHOW DATABASES privilege that can be used to control access to database names on a per-account basis. See Section 5.4.1, “Privileges Provided by MySQL”. --safe-show-database was removed in MySQL 5.5.3.

  • --safe-user-create

    Command-Line Format--safe-user-create
    Option-File Formatsafe-user-create
     Permitted Values
    Typeboolean
    DefaultFALSE

    If this option is enabled, a user cannot create new MySQL users by using the GRANT statement unless the user has the INSERT privilege for the mysql.user table or any column in the table. If you want a user to have the ability to create new users that have those privileges that the user has the right to grant, you should grant the user the following privilege:

    GRANT INSERT(user) ON mysql.user TO 'user_name'@'host_name';
    

    This ensures that the user cannot change any privilege columns directly, but has to use the GRANT statement to give privileges to other users.

  • --secure-auth

    Command-Line Format--secure-auth
    Option-File Formatsecure-auth
    Option Sets VariableYes, secure_auth
    Variable Namesecure_auth
    Variable ScopeGlobal
    Dynamic VariableYes
     Permitted Values
    Typeboolean
    DefaultFALSE

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

  • --secure-file-priv=path

    Command-Line Format--secure-file-priv=path
    Option-File Formatsecure-file-priv=path
    Option Sets VariableYes, secure_file_priv
    Variable Namesecure-file-priv
    Variable ScopeGlobal
    Dynamic VariableNo
     Permitted Values
    Typestring

    This option limits the effect of the LOAD_FILE() function and the LOAD DATA and SELECT ... INTO OUTFILE statements to work only with files in the specified directory.

  • --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-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.) See Section 7.10.3, “Concurrent Inserts”.

  • --skip-external-locking

    Do not use external locking (system locking). For more information about external locking, including conditions under which it can and cannot be used, see Section 7.10.5, “External Locking”.

    External locking has been disabled by default since MySQL 4.0.

  • --skip-event-scheduler

    Command-Line Format--skip-event-scheduler
    --disable-event-scheduler
    Option-File Formatskip-event-scheduler

    Turns the Event Scheduler OFF. This is not the same as disabling the Event Scheduler, which requires setting --event-scheduler=DISABLED; see The --event-scheduler Option, for more information.

  • --skip-grant-tables

    This option causes the server to start without using 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 plugins that were installed with the INSTALL PLUGIN statement, user-defined functions (UDFs), and scheduled events. To cause plugins to be loaded anyway, use the --plugin-load option.

    --skip-grant-tables is unavailable if MySQL was configured with the DISABLE_GRANT_OPTIONS compiler flag. See Section 2.11.4, “MySQL Source-Configuration Options”.

  • --skip-host-cache

    Do not use the internal host name cache for faster name-to-IP resolution. Instead, query the DNS server every time a client connects. See Section 7.11.5.2, “How MySQL Uses DNS”.

  • --skip-innodb

    Disable the InnoDB storage engine. In this case, the server will not start if the default storage engine is set to InnoDB. Use --default-storage-engine to set the default to some other engine if necessary.

  • --skip-name-resolve

    Do not resolve host names when checking client connections. Use only IP addresses. If you use this option, all Host column values in the grant tables must be IP addresses or localhost. See Section 7.11.5.2, “How MySQL Uses DNS”.

  • --skip-networking

    Do not listen for TCP/IP connections at all. All interaction with mysqld must be made using 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 permitted. See Section 7.11.5.2, “How MySQL Uses DNS”.

  • --skip-partition

    Command-Line Format--skip-partition
    --disable-partition
    Option-File Formatskip-partition

    Disables user-defined partitioning. Existing partitioned tables cannot be accessed when the server has been started with this option.

  • --ssl*

    Options that begin with --ssl specify whether to permit clients to connect using SSL and indicate where to find SSL keys and certificates. See Section 5.5.8.3, “SSL Command Options”.

  • --standalone

    Command-Line Format--standalone
    Option-File Formatstandalone
    Platform Specificwindows

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

  • --super-large-pages

    Standard use of large pages in MySQL attempts to use the largest size supported, up to 4MB. Under Solaris, a “super large pages” feature enables uses of pages up to 256MB. This feature is available for recent SPARC platforms. It can be enabled or disabled by using the --super-large-pages or --skip-super-large-pages option.

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

    Command-Line Format--symbolic-links
    Option-File Formatsymbolic-links

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

  • --skip-safemalloc

    Version Removed5.5.6
    Command-Line Format--skip-safemalloc
    Option-File Formatskip-safemalloc

    Previously, if MySQL was configured with full debugging support, 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 do not need it by using the --skip-safemalloc option.

    safemalloc, along with this option, was removed in MySQL 5.5.6.

  • --skip-show-database

    Command-Line Format--skip-show-database
    Option-File Formatskip-show-database
    Option Sets VariableYes, skip_show_database
    Variable Nameskip_show_database
    Variable ScopeGlobal
    Dynamic VariableNo

    With this option, the SHOW DATABASES statement is permitted only to users who have the SHOW DATABASES privilege, and the statement displays all database names. Without this option, SHOW DATABASES is permitted 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

    Command-Line Format--skip-stack-trace
    Option-File Formatskip-stack-trace

    Do not 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 MySQL Internals: Porting.

  • --skip-thread-priority

    Command-Line Format--skip-thread-priority
    Option-File Formatskip-thread-priority
    Deprecated5.1.29

    Disable using thread priorities for faster response time. This option is deprecated.

  • --slow-query-log[={0|1}]

    Command-Line Format--slow-query-log
    Option-File Formatslow-query-log
    Option Sets VariableYes, slow_query_log
    Variable Nameslow_query_log
    Variable ScopeGlobal
    Dynamic VariableYes
     Permitted Values
    Typeboolean
    DefaultOFF

    Specify the initial slow query log state. With no argument or an argument of 1, the --slow-query-log option enables the log. If omitted or given with an argument of 0, the option disables the log.

  • --socket=path

    Command-Line Format--socket=name
    Option-File Formatsocket
    Option Sets VariableYes, socket
    Variable Namesocket
    Variable ScopeGlobal
    Dynamic VariableNo
     Permitted Values
    Typefile name
    Default/tmp/mysql.sock

    On Unix, this option specifies the Unix socket file to use when listening for local connections. The default value is /tmp/mysql.sock. If this option is given, the server creates the file in the data directory unless an absolute path name is given to specify a different directory. 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...]]

    Command-Line Format--sql-mode=name
    Option-File Formatsql-mode
    Option Sets VariableYes, sql_mode
    Variable Namesql_mode
    Variable ScopeGlobal, Session
    Dynamic VariableYes
     Permitted Values
    Typeset
    Default''
    Valid ValuesALLOW_INVALID_DATES, ANSI_QUOTES, ERROR_FOR_DIVISION_BY_ZERO, HIGH_NOT_PRECEDENCE, IGNORE_SPACE, NO_AUTO_CREATE_USER, NO_AUTO_VALUE_ON_ZERO, NO_BACKSLASH_ESCAPES, NO_DIR_IN_CREATE, NO_ENGINE_SUBSTITUTION, NO_FIELD_OPTIONS, NO_KEY_OPTIONS, NO_TABLE_OPTIONS, NO_UNSIGNED_SUBTRACTION, NO_ZERO_DATE, NO_ZERO_IN_DATE, ONLY_FULL_GROUP_BY, PAD_CHAR_TO_FULL_LENGTH, PIPES_AS_CONCAT, REAL_AS_FLOAT, STRICT_ALL_TABLES, STRICT_TRANS_TABLES

    Set the SQL mode. See Section 5.1.7, “Server SQL Modes”.

  • --sysdate-is-now

    Command-Line Format--sysdate-is-now
    Option-File Formatsysdate-is-now
     Permitted Values
    Typeboolean
    DefaultFALSE

    SYSDATE() by default returns the time at which it executes, not the time at which the statement in which it occurs begins executing. This differs from the behavior of NOW(). This option causes SYSDATE() to be an alias for NOW(). For information about the implications for binary logging and replication, see the description for SYSDATE() in Section 11.7, “Date and Time Functions” and for SET TIMESTAMP in Section 5.1.4, “Server System Variables”.

  • --tc-heuristic-recover={COMMIT|ROLLBACK}

    Command-Line Format--tc-heuristic-recover=name
    Option-File Formattc-heuristic-recover
     Permitted Values
    Typeenumeration
    Valid ValuesCOMMIT, RECOVER

    The type of decision to use in the heuristic recovery process. Currently, this option is unused.

  • --temp-pool

    Command-Line Format--temp-pool
    Option-File Formattemp-pool
     Permitted Values
    Typeboolean
    DefaultTRUE

    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. This option is ignored except on Linux.

  • --transaction-isolation=level

    Command-Line Format--transaction-isolation=name
    Option-File Formattransaction-isolation
     Permitted Values
    Typeenumeration
    Valid ValuesREAD-UNCOMMITTED, READ-COMMITTED, REPEATABLE-READ, SERIALIZABLE

    Sets the default transaction isolation level. The level value can be READ-UNCOMMITTED, READ-COMMITTED, REPEATABLE-READ, or SERIALIZABLE. See Section 12.3.6, “SET TRANSACTION Syntax”.

  • --tmpdir=path, -t path

    Command-Line Format--tmpdir=path
    -t
    Option-File Formattmpdir
    Option Sets VariableYes, tmpdir
    Variable Nametmpdir
    Variable ScopeGlobal
    Dynamic VariableNo
     Permitted Values
    Typefile name

    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. If the MySQL server is acting as a replication slave, you should not set --tmpdir to point to a directory on a memory-based file system or to a directory that is cleared when the server host restarts. For more information about the storage location of temporary files, see Section C.5.4.4, “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}

    Command-Line Format--user=name
    -u name
    Option-File Formatuser
     Permitted Values
    Typestring

    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 5.3.1, “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.

  • --verbose, -v

    Use this option with the --help option for detailed help.

  • --version, -V

    Display version information and exit.

You can assign a value to a server system variable 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 you assign a value to a variable, MySQL might automatically correct the value to stay within a given range, or adjust the value to the closest permissible value if only certain values are permitted.

If you want to restrict the maximum value to which a variable can be set at runtime with SET, you can define this by using the --maximum-var_name=value command-line option.

You can change the values of most system variables for a running server with the SET statement. See Section 12.4.4, “SET Syntax”.

Section 5.1.4, “Server System Variables”, provides a full description for all variables, and additional information for setting them at server startup and runtime. Section 7.11.2, “Tuning Server Parameters”, includes information on optimizing the server by tuning system variables.

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