(mysql.info) program-variables

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(mysql.info) program-options

 
 4.3.4 Using Options to Set Program Variables
 --------------------------------------------
 
 Many MySQL programs have internal variables that can be set at runtime.
 Program variables are set the same way as any other long option that
 takes a value. For example, `mysql' has a `max_allowed_packet' variable
 that controls the maximum size of its communication buffer. To set the
 `max_allowed_packet' variable for `mysql' to a value of 16MB, use
 either of the following commands:
 
      shell> mysql --max_allowed_packet=16777216
      shell> mysql --max_allowed_packet=16M
 
 The first command specifies the value in bytes. The second specifies
 the value in megabytes. For variables that take a numeric value, the
 value can be given with a suffix of `K', `M', or `G' (either uppercase
 or lowercase) to indicate a multiplier of 1024, 10242 or 10243. (For
 example, when used to set `max_allowed_packet', the suffixes indicate
 units of kilobytes, megabytes, or gigabygtes.)
 
 In an option file, variable settings are given without the leading
 dashes:
 
      [mysql]
      max_allowed_packet=16777216
 
 Or:
 
      [mysql]
      max_allowed_packet=16M
 
 If you like, underscores in a variable name can be specified as dashes.
 The following option groups are equivalent. Both set the size of the
 server's key buffer to 512MB:
 
      [mysqld]
      key_buffer_size=512M
 
      [mysqld]
      key-buffer-size=512M
 
 * Before MySQL 4.0.2, the only syntax for setting program
 variables was -set-variable=OPTION=VALUE (or set-variable=OPTION=VALUE
 in option files). This syntax still is recognized, but is deprecated as
 of MySQL 4.0.2.
 
 Many server system variables can also be set at runtime. For details,
 see  dynamic-system-variables.
 

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