SET Statements The following discussion describes the syntax options for setting and persisting system variables: SET GLOBAL max_connections = 1000; SET @@GLOBAL.max_connections = 1000; •To assign a value to a global system variable, precede the variable name by the  GLOBAL  keyword or the @@GLOBAL.  qualifier: •To assign a value to a session system variable, precede the variable name by the  SESSION  or  LOCAL keyword, by the  @@SESSION. ,  @@LOCAL. , or  @@  qualifier, or by no keyword or no modifier at all: SET SESSION sql_mode = ’TRADITIONAL’; SET LOCAL sql_mode = ’TRADITIONAL’; SET @@SESSION.sql_mode = ’TRADITIONAL’; SET @@LOCAL.sql_mode = ’TRADITIONAL’; SET @@sql_mode = ’TRADITIONAL’; SET sql_mode = ’TRADITIONAL’; A client can change its own session variables, but not those of any other client. SET PERSIST max_connections = 1000; SET @@PERSIST.max_connections = 1000; •To persist a global system variable to the  mysqld-auto.cnf  option file in the data directory, precede the variable name by the  PERSIST  keyword or the  @@PERSIST.  qualifier: •To persist a global system variable to the  mysqld-auto.cnf  file without setting the global variable runtime value, precede the variable name by the  PERSIST_ONLY  keyword or the  @@PERSIST_ONLY. qualifier: This  SET  syntax enables you to make configuration changes at runtime that also persist across server restarts. Like  SET GLOBAL ,  SET PERSIST  sets the global variable runtime value, but also writes the variable setting to the  mysqld-auto.cnf  file (replacing any existing variable setting if there is one). SET PERSIST_ONLY back_log = 100; SET @@PERSIST_ONLY.back_log = 100; Like  PERSIST ,  PERSIST_ONLY  writes the variable setting to  mysqld-auto.cnf . However, unlike  PERSIST ,  PERSIST_ONLY  does not modify the global variable runtime value. This makes PERSIST_ONLY  suitable for configuring read-only system variables that can be set only at server startup. To set a global system variable value to the compiled-in MySQL default value or a session system variable to the current corresponding global value, set the variable to the value  DEFAULT . For example, the following two statements are identical in setting the session value of  max_join_size  to the current global value: SET @@SESSION.max_join_size = DEFAULT; SET @@SESSION.max_join_size = @@GLOBAL.max_join_size; Using  SET  to persist a global system variable to a value of  DEFAULT  or to its literal default value assigns the variable its default value and adds a setting for the variable to  mysqld-auto.cnf . To remove the variable from the file, use  RESET PERSIST . Some system variables cannot be persisted or are persist-restricted. See Section 5.1.9.4, “Nonpersistible and Persist-Restricted System Variables” . A system variable implemented by a plugin can be persisted if the plugin is installed when the  SET statement is executed. Assignment of the persisted plugin variable takes effect for subsequent server 2908