接到報故，查看mysql數據庫以下參數
1、innodb_buffer_pool_size
2、max_connections
該參數定義了數據緩沖區buffer pool大小，類似於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)
那么如何設置該參數大小呢？首先查看運行時buffer pool相關數據指標：
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)
上述三項指標的含義如下：
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
計算Innodb_buffer_pool_pages_data/Innodb_buffer_pool_pages_total*100%
當結果 > 95% 則增加 innodb_buffer_pool_size， 建議使用物理內存的 75%
當結果 < 95% 則減少 innodb_buffer_pool_size，
建議設置大小為： Innodb_buffer_pool_pages_data* Innodb_page_size * 1.05 / (1024*1024*1024)
--------------------------------------------------------------------------------------------------------------------------------------------------------
MySQL服務器的連接數並不是要達到最大的100%為好，還是要具體問題具體分析，下面就對MySQL服務器最大連接數的合理設置進行了詳盡的分析，供您參考。
我們經常會遇見“MySQL: ERROR 1040: Too many connections”的情況，一種是訪問量確實很高，MySQL服務器抗不住，這個時候就要考慮增加從服務器分散讀壓力，另外一種情況是MySQL配置文件中max_connections值過小：
mysql> show variables like 'max_connections';
+-----------------+-------+
| Variable_name | Value |
+-----------------+-------+
| max_connections | 256 |
+-----------------+-------+
這台MySQL服務器最大連接數是256，然后查詢一下服務器響應的最大連接數：
mysql> show global status like 'Max_used_connections';
MySQL服務器過去的最大連接數是245，沒有達到服務器連接數上限256，應該沒有出現1040錯誤，比較理想的設置是：
Max_used_connections / max_connections * 100% ≈ 85%
最大連接數占上限連接數的85%左右，如果發現比例在10%以下，MySQL服務器連接上線就設置得過高了。