max_user_connections参数设置试验

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--查看当前max_user_connections连接参数值为0,表示没有限制.
mysql> show global variables like %connect%; +--------------------------+-----------------+ | Variable_name | Value | +--------------------------+-----------------+ | character_set_connection | utf8 | | collation_connection | utf8_general_ci | | connect_timeout | 10 | | init_connect | | | max_connect_errors | 10 | | max_connections | 160 | | max_user_connections | 0 | +--------------------------+-----------------+ 7 rows in set (0.00 sec) --设置max_user_connections值为2 mysql> set global max_user_connections=2; Query OK, 0 rows affected (0.00 sec) --查看设置是否生效 mysql> show global variables like %connect%; +--------------------------+-----------------+ | Variable_name | Value | +--------------------------+-----------------+ | character_set_connection | utf8 | | collation_connection | utf8_general_ci | | connect_timeout | 10 | | init_connect | | | max_connect_errors | 10 | | max_connections | 160 | | max_user_connections | 2 | +--------------------------+-----------------+ 7 rows in set (0.00 sec) --退出数据库 mysql> exit Bye --登录数据库 C:\Users\ArcerZhang>mysql -uroot -parcerzhang Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 7 Server version: 5.5.28 MySQL Community Server (GPL) Copyright (c) 2000, 2012, 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. --查看数据库 mysql> show global variables like %connect%; +--------------------------+-----------------+ | Variable_name | Value | +--------------------------+-----------------+ | character_set_connection | utf8 | | collation_connection | utf8_general_ci | | connect_timeout | 10 | | init_connect | | | max_connect_errors | 10 | | max_connections | 160 | | max_user_connections | 2 | +--------------------------+-----------------+ 7 rows in set (0.00 sec) mysql>

二、登录第一个窗口

C:\Users\ArcerZhang>mysql -uroot -parcerzhang
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 8
Server version: 5.5.28 MySQL Community Server (GPL)

Copyright (c) 2000, 2012, 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>

三、登录第二个窗口

C:\Users\ArcerZhang>mysql -uroot -parcerzhang
ERROR 1203 (42000): User root already has more than max_user_connections active connections

C:\Users\ArcerZhang>

四、结论

当max_user_connections设置为2时,使用一个用户登录mysql server,当开启第二窗口登录时,就会报错了.而且第一个试验窗口也算是一个用户登录.

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