autotrace統計資訊解釋

    autotrace統計資訊解釋

SQL> set autotrace traceonly

SQL> set timing on

SQL> select * from employee;

已選擇9行。

已用時間:  00: 00: 00.01

執行計劃

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| Id  | Operation         | Name     | Rows  | Bytes | Cost (%CPU)|

---------------------------------------------------------------------------------------------------

|   0 | SELECT STATEMENT  |          |     9 |    81 |     3 (0)|

|   1 |  TABLE ACCESS FULL| EMPLOYEE |     9 |    81 |     3 (0)|

---------------------------------------------------------------------------------------------------

統計資訊

----------------------------------------------------------

          0  recursive calls

          0  db block gets

          8  consistent gets

          0  physical reads

          0  redo size

        583  bytes sent via SQL*Net to client

        350  bytes received via SQL*Net from client

          2  SQL*Net roundtrips to/from client

          0  sorts (memory)

          0  sorts (disk)

          9  rows processed

recursive calls ：遞歸調用。一般原因：dictionary cache未命中；動态存儲擴充；PL/SQL語句

db block gets ：從buffer cache中讀取的block的數量(多為update)    

consistent gets： 資料庫緩沖區中讀取的資料塊的個數    

physical reads： 從磁盤讀取的block的數量    

redo size： DML生成的redo的大小    

BYTES SENT VIA SQL*NET TO CLIENT：伺服器通過SQL*NET向用戶端發送的位元組數

BYTES RECEIVED VIA SQL*NET FROM CLIENT：用戶端向SQL*NET發送的位元組數

SQL*NET ROUNDTRIPS TO/FROM CLIENT：伺服器與CLIENT通信的次數

sorts (memory) ：在記憶體執行的排序量    

sorts (disk) ：在磁盤上執行的排序量 

rows processed ：傳回記錄數