通过show status 来优化MySQL数据库 from lxneng

1\. 查看MySQL服务器配置信息 mysql> show variables; 2\. 查看MySQL服务器运行的各种状态值 mysql> show global status; 3\. 慢查询 mysql> show variables like '%slow%'; +------------------+-------+ | Variable_name | Value | +------------------+-------+ | log_slow_queries | OFF | | slow_launch_time | 2 | +------------------+-------+ mysql> show global status like '%slow%'; +---------------------+-------+ | Variable_name | Value | +---------------------+-------+ | Slow_launch_threads | 0 | | Slow_queries | 279 | +---------------------+-------+ 配置中关闭了记录慢查询（最好是打开，方便优化），超过2秒即为慢查询，一共有279条慢查询 4\. 连接数 mysql> show variables like 'max_connections'; +-----------------+-------+ | Variable_name | Value | +-----------------+-------+ | max_connections | 500 | +-----------------+-------+ mysql> show global status like 'max_used_connections'; +----------------------+-------+ | Variable_name | Value | +----------------------+-------+ | Max_used_connections | 498 | +----------------------+-------+ 设置的最大连接数是500，而响应的连接数是498 max_used_connections / max_connections * 100% = 99.6% （理想值 ≈ 85%） 5\. key_buffer_size key_buffer_size是对MyISAM表性能影响最大的一个参数, 不过数据库中多为Innodb mysql> show variables like 'key_buffer_size'; +-----------------+----------+ | Variable_name | Value | +-----------------+----------+ | key_buffer_size | 67108864 | +-----------------+----------+ mysql> show global status like 'key_read%'; +-------------------+----------+ | Variable_name | Value | +-------------------+----------+ | Key_read_requests | 25629497 | | Key_reads | 66071 | +-------------------+----------+ 一共有25629497个索引读取请求，有66071个请求在内存中没有找到直接从硬盘读取索引，计算索引未命中缓存的概率： key_cache_miss_rate ＝ Key_reads / Key_read_requests * 100% =0.27% 需要适当加大key_buffer_size mysql> show global status like 'key_blocks_u%'; +-------------------+-------+ | Variable_name | Value | +-------------------+-------+ | Key_blocks_unused | 10285 | | Key_blocks_used | 47705 | +-------------------+-------+ Key_blocks_unused表示未使用的缓存簇(blocks)数，Key_blocks_used表示曾经用到的最大的blocks数 Key_blocks_used / (Key_blocks_unused + Key_blocks_used) * 100% ≈ 18% （理想值 ≈ 80%） 6\. 临时表 mysql> show global status like 'created_tmp%'; +-------------------------+---------+ | Variable_name | Value | +-------------------------+---------+ | Created_tmp_disk_tables | 4184337 | | Created_tmp_files | 4124 | | Created_tmp_tables | 4215028 | +-------------------------+---------+ 每次创建临时表，Created_tmp_tables增加，如果是在磁盘上创建临时表，Created_tmp_disk_tables也增加,Created_tmp_files表示MySQL服务创建的临时文件文件数： Created_tmp_disk_tables / Created_tmp_tables * 100% ＝ 99% （理想值<= 25%） mysql> show variables where Variable_name....