最近忙得不可開交,項目進入了cut over階段,壓力之大,前所未有。我的任務就是,負責優化long running的SQL,讓其可以在3小時以內完成。昨天就出現一個Long running 的SQL,它跑了16小時,經過2小時的奮鬥,終於把它優化到了2小時10分鐘。
雖然那個Long running SQL 與統計信息無關,但是我還是提出要確保統計信息的準確性。作爲DBA,我必須定製出收集統計信息的策略,以及相關腳本,下面就是一個關於確保統計信息準確性的腳本,拿出來分享一下。
DECLARE
CURSOR STALE_TABLE IS
SELECT OWNER,
SEGMENT_NAME,
CASE
WHEN SIZE_GB < 0.5 THEN
30
WHEN SIZE_GB >= 0.5 AND SIZE_GB < 1 THEN
20
WHEN SIZE_GB >= 1 AND SIZE_GB < 5 THEN
10
WHEN SIZE_GB >= 5 AND SIZE_GB < 10 THEN
5
WHEN SIZE_GB >= 10 THEN
1
END AS PERCENT,
8 AS DEGREE
FROM (SELECT OWNER,
SEGMENT_NAME,
SUM(BYTES / 1024 / 1024 / 1024) SIZE_GB
FROM DBA_SEGMENTS
WHERE OWNER = 'ADWU_OPTIMA_AP11'
AND SEGMENT_NAME IN
(SELECT /*+ UNNEST */ DISTINCT TABLE_NAME
FROM DBA_TAB_STATISTICS
WHERE (LAST_ANALYZED IS NULL OR STALE_STATS = 'YES')
AND OWNER = 'ADWU_OPTIMA_AP11')
GROUP BY OWNER, SEGMENT_NAME);
BEGIN
DBMS_STATS.FLUSH_DATABASE_MONITORING_INFO;
FOR STALE IN STALE_TABLE LOOP
DBMS_STATS.GATHER_TABLE_STATS(OWNNAME => STALE.OWNER,
TABNAME => STALE.SEGMENT_NAME,
ESTIMATE_PERCENT => STALE.PERCENT,
METHOD_OPT => 'for all columns size repeat',
DEGREE => 8,
GRANULARITY => 'ALL',
CASCADE => TRUE);
END LOOP;
END;
/
根據實際情況,可以選擇每天晚上在數據庫不繁忙的時候運行上述腳本。
原帖自:http://blog.csdn.net/robinson1988/article/details/6321537