查看mysql数据库以下参数
1、innodb_buffer_pool_size
2、max_connections
该参数定义了数据缓冲区buffer pool大小，类似于oracle的db_cache_size mysql> show global variables like 'innodb_buffer_pool_size'; +-------------------------+-----------+ | Variable_name | Value | +-------------------------+-----------+ | innodb_buffer_pool_size | 134217728 | +-------------------------+-----------+ 1 row in set (0.00 sec) 那么如何设置该参数大小呢？首先查看运行时buffer pool相关数据指标： mysql> show global status like 'Innodb_buffer_pool_pages_data'; +-------------------------------+-------+ | Variable_name | Value | +-------------------------------+-------+ | Innodb_buffer_pool_pages_data | 314 | +-------------------------------+-------+ 1 row in set (0.00 sec) mysql> show global status like 'Innodb_buffer_pool_pages_total'; +--------------------------------+-------+ | Variable_name | Value | +--------------------------------+-------+ | Innodb_buffer_pool_pages_total | 8191 | +--------------------------------+-------+ 1 row in set (0.00 sec) mysql> show global status like 'Innodb_page_size'; +------------------+-------+ | Variable_name | Value | +------------------+-------+ | Innodb_page_size | 16384 | +------------------+-------+ 1 row in set (0.00 sec) 上述三项指标的含义如下： Innodb_buffer_pool_pages_data The number of pages in the InnoDB buffer pool containing data. The number includes both dirty and clean pages. Innodb_buffer_pool_pages_total The total size of the InnoDB buffer pool, in pages. Innodb_page_size InnoDB page size (default 16KB). Many values are counted in pages; the page size enables them to be easily converted to bytes 计算Innodb_buffer_pool_pages_data/Innodb_buffer_pool_pages_total*100% 当结果 > 95% 则增加 innodb_buffer_pool_size， 建议使用物理内存的 75% 当结果 < 95% 则减少 innodb_buffer_pool_size， 建议设置大小为： Innodb_buffer_pool_pages_data* Innodb_page_size * 1.05 / (1024*1024*1024)
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MySQL服务器的连接数并不是要达到最大的100%为好，还是要具体问题具体分析，下面就对MySQL服务器最大连接数的合理设置进行了详尽的分析，供您参考。
我们经常会遇见“MySQL: ERROR 1040: Too many connections”的情况，一种是访问量确实很高，MySQL服务器抗不住，这个时候就要考虑增加从服务器分散读压力，另外一种情况是MySQL配置文件中max_connections值过小：
mysql> show variables like 'max_connections'; +-----------------+-------+ | Variable_name | Value | +-----------------+-------+ | max_connections | 256 | +-----------------+-------+
这台MySQL服务器最大连接数是256，然后查询一下服务器响应的最大连接数：
mysql> show global status like 'Max_used_connections';
MySQL服务器过去的最大连接数是245，没有达到服务器连接数上限256，应该没有出现1040错误，比较理想的设置是：
Max_used_connections / max_connections * 100% ≈ 85%
最大连接数占上限连接数的85%左右，如果发现比例在10%以下，MySQL服务器连接上线就设置得过高了。
