tailieunhanh - MySQL Administrator's Bible- P13

MySQL Administrator's Bible- P13: Với tập trung đặc biệt vào việc phát hành lớn tiếp theo của MySQL, nguồn tài nguyên này cung cấp một khuôn khổ vững chắc cho bất cứ ai mới vào MySQL hoặc chuyển từ một nền tảng cơ sở dữ liệu, cũng như các quản trị MySQL kinh nghiệm. Các bộ đôi tác giả cao hồ sơ cung cấp bảo hiểm thiết yếu của các nguyên tắc cơ bản của phạm vi bảo hiểm cơ sở dữ liệu quản lý, bao gồm cả cách tiếp cận độc đáo MySQL của các tính năng cơ sở. | Measuring Performance 17 For some status variables such as Slave_running the current output is enough information either the slave is running or it is not. The Threads_connected status variable shows how many threads are currently connected. However for many status variables there is more to be done than simply looking at the value of each variable. For example the Slow_queries status variable provides a count of how many slow queries the system has logged mysql SHOW GLOBAL STATUS LIKE Slow_queries ---------------- ------- Variable_name Value ---------------- ------- Slow_queries 1073 ---------------- ------- 1 row in set sec Is it good or bad that there have been 1073 slow queries You should investigate and optimize all the slow queries that are logged see the mysqldumpslow and mysqlsla tools discussed later in this chapter for how to find slow queries and see Chapter 18 for how to analyze queries. When determining the health of a system the important data is how frequently slow queries are happening. The Uptime status variable shows how long in seconds that particular mysqld has been running mysql SHOW GLOBAL STATUS WHERE Variable_name Slow_queries - OR Variable_name uptime ---------------- ------- Variable_name Value ---------------- ------- Slow_queries 1073 Uptime 10906 ---------------- ------- 2 rows in set sec The server has been up for 10906 seconds or roughly seven and a half days The rate of slow queries is an average of about one slow query every 10 seconds. Ideally you would like to be able to see the rate of change over time. For example the slow query information you saw earlier would indicate a problem in a database that usually has one slow query every hour the database administrator would be celebrated in a database that usually has one slow query every second. Establishing a baseline for a system s status and comparing over time will make patterns evident and shows where problems may lurk. One way to establish a baseline is to compare .