达梦数据库的整体负载变化查看

挖掘略显薄弱的系统统计信息

SQL> desc v$sysstat
NAME     TYPE$        NULLABLE
-------- ------------ --------
ID       INTEGER      Y
CLASSID  INTEGER      Y
NAME     VARCHAR(128) Y
STAT_VAL BIGINT       Y

-- 创建监控表
drop table sysstat_baseline ;
CREATE TABLE sysstat_baseline AS
SELECT s.*, SYSDATE as capture_time
FROM v$sysstat s;


-- 每隔5分钟插入一次
insert into sysstat_baseline SELECT s.*, SYSDATE as capture_time FROM v$sysstat s;


-- 查询增量
select * from (
SELECT 
  ss.name,
  (ss.STAT_VAL - bl.STAT_VAL) as delta_STAT_VAL,
  ROUND((ss.STAT_VAL - bl.STAT_VAL) / 
        datediff(ss,capture_time,sysdate)/60 , 2) as per_fen
FROM v$sysstat ss
JOIN sysstat_baseline bl ON ss.id = bl.id
WHERE ss.STAT_VAL != bl.STAT_VAL) order by PER_FEN desc limit 20;


-- Top 10增量统计
WITH deltas AS (
  SELECT 
    s.name,
    s.STAT_VAL - LAG(s.STAT_VAL) OVER (PARTITION BY s.id ORDER BY s.capture_time) as delta 
  FROM sysstat_baseline s
  WHERE s.STAT_VAL > 0
)
SELECT * FROM (
  SELECT name, delta, 
         RANK() OVER (ORDER BY delta DESC) as rank
  FROM deltas
  WHERE delta IS NOT NULL
)
WHERE rank <= 10;