MySQL之performance_schema数据库的max变量含义

1.max_connections

    List-1 大致意思是MySQL容许的最大链接

mysql> select * from global_variables where variable_name like "max_connections";
+-----------------+----------------+
| VARIABLE_NAME   | VARIABLE_VALUE |
+-----------------+----------------+
| max_connections | 600            |
+-----------------+----------------+
1 row in set (0.00 sec)

2.max_user_connections

    List-2 大致意思是一个用户链接到数据库的最大链接数，为0应该是表示不限制，设置这个变量的值能够防止一个用户用完全部数据库容许的最大链接。

mysql> select * from global_variables where variable_name like "max_user_connections";
+----------------------+----------------+
| VARIABLE_NAME        | VARIABLE_VALUE |
+----------------------+----------------+
| max_user_connections | 0              |
+----------------------+----------------+
1 row in set (0.00 sec)

3.max_connect_errors

    List-3

mysql> select * from global_variables where variable_name like "max_connect_errors";
+--------------------+----------------+
| VARIABLE_NAME      | VARIABLE_VALUE |
+--------------------+----------------+
| max_connect_errors | 100            |
+--------------------+----------------+
1 row in set (0.01 sec)

    此值为100时，意味着若是某一客户端尝试链接此MySQL服务器，可是失败（如密码错误等等）100次，则MySQL会无条件强制阻止此客户端链接。