oracle培訓講義-文庫吧
2025-04-01 12:33 本頁面
【正文】 9 sorts (memory) 0 sorts (disk) 12 rows processedSQL /ENAME TEST SMITH 6ALLEN 6WARD 6JONES 6MARTIN 6BLAKE 6CLARK 6KING 6TURNER 6JAMES 6FORD 6MILLER 6已選擇12行。Execution Plan 0 SELECT STATEMENT Optimizer=CHOOSE 1 0 TABLE ACCESS (FULL) OF 39。EMP39。Statistics 12 recursive calls 0 db block gets 92 consistent gets 0 physical reads 0 redo size 579 bytes sent via SQL*Net to client 503 bytes received via SQL*Net from client 2 SQL*Net roundtrips to/from client 0 sorts (memory) 0 sorts (disk) 12 rows processedSQL /ENAME TEST SMITH 6ALLEN 6WARD 6JONES 6MARTIN 6BLAKE 6CLARK 6KING 6TURNER 6JAMES 6FORD 6MILLER 6已選擇12行。Execution Plan 0 SELECT STATEMENT Optimizer=CHOOSE 1 0 TABLE ACCESS (FULL) OF 39。EMP39。Statistics 12 recursive calls 0 db block gets 92 consistent gets 0 physical reads 0 redo size 579 bytes sent via SQL*Net to client 503 bytes received via SQL*Net from client 2 SQL*Net roundtrips to/from client 0 sorts (memory) 0 sorts (disk) 12 rows processed216。 side effect from modification：由于triggers、基于函數(shù)的索引引起。216。 space request：DMT表空間中的表要求空間時，會引起較多的recursive calls，通過使用LMT，可以顯著減少這種recursive calls，而LMT中的recursive calls主要是由于驗證quota權限引起?？梢酝ㄟ^實驗驗證上面的說法(實驗步驟見Effective Oracle by Design pp101)。252。 db block gets and consistent getsdb block get是以current mode讀取的數(shù)據(jù)塊數(shù)，通常是由于數(shù)據(jù)修改而引起，consistent gets是以consistent mode讀取的數(shù)據(jù)塊數(shù)，通常由于select操作引起。我們關注的是這兩個數(shù)量之和，即邏輯I/O的數(shù)量，邏輯I/O也代表了對緩存加上latch的數(shù)量，邏輯I/O越少，越好。The less logical I/O we can do,the better。我們可以通過設置合適的arraysize(許多方法中的一個，適用于sql*plus)來降低邏輯I/O數(shù)量，ODBC，JDBC也有類似的設置。Array size：SQL conn system/oracle@catalog已連接。SQL grant dba to scott。授權成功。SQL conn scott/tiger@catalog已連接。SQL drop table t。表已丟棄。SQL create table t 2 as 3 select * from all_objects。表已創(chuàng)建。SQL select count(*) from t。 COUNT(*)6219已選擇6219行。SQL set autotrace traceonly statisticsSQL select * from t。已選擇6219行。Statistics 0 recursive calls 0 db block gets 491 consistent gets 0 physical reads 0 redo size 357171 bytes sent via SQL*Net to client 5057 bytes received via SQL*Net from client 416 SQL*Net roundtrips to/from client 0
教學教案相關推薦
鄂ICP備17016276號-1