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MySQL Variables open_files_limit 数据库 参数变量解释及正确配置使用

本站中文解释

open_files_limit参数能够控制MySQL进程能够打开的文件数量。它能够控制全局变量 max_open_files 的值，确保MySQL能够正确地打开所需要数量的文件。

要设置open_files_limit参数，需要编辑MySQL配置文件my.cnf，在[mysqld]部分添加 open_files_limit = N (N为你想要设置的数字)， 然后运行show variables like ‘open_files_limit’ 命令来查看已设置的参数值。

官方英文解释

open_files_limit

Command-Line Format --open-files-limit=#
System Variable open_files_limit
Scope Global
Dynamic No
Type Integer
Default Value 5000, with possible adjustment
Minimum Value 0
Maximum Value platform dependent

The number of file descriptors available to
mysqld from the operating system:

  • At startup, mysqld reserves descriptors
    with setrlimit(), using the value
    requested at by setting this variable directly or by using
    the --open-files-limit
    option to mysqld_safe. If
    mysqld produces the error Too
    many open files    , try increasing the
    open_files_limit value.
    Internally, the maximum value for this variable is the
    maximum unsigned integer value, but the actual maximum is
    platform dependent.

  • At runtime, the value of
    open_files_limit
    indicates the number of file descriptors actually
    permitted to mysqld by the operating
    system, which might differ from the value requested at
    startup. If the number of file descriptors requested
    during startup cannot be allocated,
    mysqld writes a warning to the error
    log.

The effective
open_files_limit value is
based on the value specified at system startup (if any) and
the values of max_connections
and table_open_cache, using
these formulas:

  • 10 + max_connections + (table_open_cache *
    2)

  • max_connections * 5

  • The operating system limit if that limit is positive but
    not Infinity.

  • If the operating system limit is Infinity:
    open_files_limit value if specified at
    startup, 5000 if not.

The server attempts to obtain the number of file descriptors
using the maximum of those values. If that many descriptors
cannot be obtained, the server attempts to obtain as many as
the system permits.

The effective value is 0 on systems where MySQL cannot change
the number of open files.

On Unix, the value cannot be set greater than the value
displayed by the ulimit -n command. On
Linux systems using systemd, the value
cannot be set greater than LimitNOFile
(this is DefaultLimitNOFILE, if
LimitNOFile is not set); otherwise, on
Linux, the value of open_files_limit cannot
exceed ulimit -n.


数据运维技术 » MySQL Variables open_files_limit 数据库 参数变量解释及正确配置使用
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