MySQL parameter files and parameters

MySQL parameter file is----MY.CNF

2. How to determine which of the database reads, the command gives the answer
   

   [[email protected] home]# MySQL--help |grep my.cnf
   Order of preference, MY.CNF, $MYSQL _tcp_port,
   /ETC/MY.CNF/ETC/MYSQL/MY.CNF/USR/LOCAL/MYSQL/ETC/MY.CNF ~/.my.cnf
   [Email protected] home]#

4. Parameters are prepared for the client, some for the server

   [Email protected] home]# CAT/ETC/MY.CNF | Grep-v "^#"
   

   [Client]

   port=3306
   

   [Mysqld]
   Datadir=/opt/mysql/data

   Basedir =/usr/local/mysql
   Socket=/usr/local/mysql/mysql.sock
   User=mysql
   Character_set_server=utf8
   server_id = 12
   Join_buffer_size = 128M
   Sort_buffer_size = 2M
   Pid-file=/opt/mysql/data/mysqld.pid
   [Email protected] home]#

6. What is a parameter?

   This is like a bond with a relationship like read_buffer_size=12m Read_buffer_size is a key 12M means

   Divided into two types of dynamic and static (read-only), can also be divided into global and local, dynamic can be modified but only in the entire life cycle of MySQL server, after the next reboot will be re-loaded according to the parameter configuration file, so to permanently take effect or modify the configuration file, Local only valid for the current session, global for all re-up sessions, dynamic modification parameters using Set [Global] Variables=key.

7. View parameters

   You can use show variables like "Variables_name" SELECT @ @session. variables_name SELECT @ @global. variables_name

   If you view Read_buffer_size

   Mysql> set read_buffer_size=524288;
   Query OK, 0 rows affected (0.07 sec)
   
   mysql> SELECT @ @session. read_buffer_size;
   +----------------------------+
   | @ @session. read_buffer_size |
   +----------------------------+
   |                      524288 |
   +----------------------------+
   1 row in Set (0.00 sec)
   
   mysql> SELECT @ @global. read_buffer_size;
   +---------------------------+
   | @ @global. read_buffer_size |
   +---------------------------+
   |                     131072 |
   +---------------------------+
   1 row in Set (0.00 sec)

   Mysql> Show variables like "read_buffer_size%";
   +------------------+--------+
   | variable_name | Value |
   +------------------+--------+
   | Read_buffer_size | 524288 |
   +------------------+--------+
   1 row in Set (0.00 sec)
   
   You can see the same set of Read_buffer_size but the session and global are different because I didn't add global when I set it up.

9. What happens if I change a static parameter?

   mysql> set global datadir= '/opt ';
   ERROR 1238 (HY000): Variable ' DataDir ' is a read only Variable
   Mysql>
   
   

This article is from "Yun Weibang" blog, please be sure to keep this source http://aklaus.blog.51cto.com/9724632/1632766

MySQL parameter files and parameters