MySQL备份与恢复（8）不重启数据库修改数据库参数

一、不重启数据库修改数据库参数，但是要求重启后还能生效

　　　　需要先修改数据库的参数，然后再修改配置文件的参数，这样数据库重启依然生效

[root@localhost bak]# grep key_buffer /etc/my.cnf 
key_buffer_size = 16K
key_buffer_size = 8M
[root@localhost bak]# mysql -uroot -pdubin 
Welcome to the MySQL monitor.  Commands end with ; or g.
Your MySQL connection id is 110
Server version: 5.5.32-log Source distribution

Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.

mysql> show variables like 'key_buffer%';
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| key_buffer_size | 16384 |
+-----------------+-------+
1 row in set (0.00 sec)

mysql> set global key_buffer_size=1024*1024*32;
Query OK, 0 rows affected (0.00 sec)

mysql> show variables like 'key_buffer%';
+-----------------+----------+
| Variable_name   | Value    |
+-----------------+----------+
| key_buffer_size | 33554432 |
+-----------------+----------+
1 row in set (0.00 sec)

mysql> quit
Bye
[root@localhost bak]# mysql -uroot -pdubin 
Welcome to the MySQL monitor.  Commands end with ; or g.
Your MySQL connection id is 111
Server version: 5.5.32-log Source distribution

Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.

mysql> show variables like 'key_buffer%';
+-----------------+----------+
| Variable_name   | Value    |
+-----------------+----------+
| key_buffer_size | 33554432 |
+-----------------+----------+
1 row in set (0.00 sec)

mysql> quit
Bye
[root@localhost bak]# /etc/init.d/mysqld restart
Shutting down MySQL.... SUCCESS! 
Starting MySQL.^[[A......... SUCCESS! 
[root@localhost bak]# mysql -uroot -pdubin 
Welcome to the MySQL monitor.  Commands end with ; or g.
Your MySQL connection id is 1
Server version: 5.5.32-log Source distribution

Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.

mysql> show variables like 'key_buffer%';
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| key_buffer_size | 16384 |
+-----------------+-------+
1 row in set (0.00 sec)

mysql> set global key_buffer_size=1024*32;
Query OK, 0 rows affected (0.00 sec)

mysql> quit
Bye
[root@localhost bak]# vi /etc/my.cnf 
[root@localhost bak]# /etc/init.d/mysqld restart
Shutting down MySQL. SUCCESS! 
Starting MySQL.. SUCCESS! 
[root@localhost bak]# mysql -uroot -pdubin 
Welcome to the MySQL monitor.  Commands end with ; or g.
Your MySQL connection id is 1
Server version: 5.5.32-log Source distribution

Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.

mysql> show variables like 'key_buffer%';
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| key_buffer_size | 32768 |
+-----------------+-------+
1 row in set (0.00 sec)