statspack报告里面的recursive cpu usage比较高是怎么回事？

Question

recursive cpu usage到底是什么东东？什么样的原因容易造成其过大？下面是报告部份
Load Profile
~~~~~~~~~~~~                            Per Second       Per Transaction
                                   ---------------       ---------------
                  Redo size:            413,860.03             17,536.65
              Logical reads:             22,521.44                954.31
              Block changes:              2,359.97                100.00
             Physical reads:                611.52                 25.91
            Physical writes:                 66.12                  2.80
                 User calls:                 40.39                  1.71
                     Parses:                 40.51                  1.72
                Hard parses:                  2.01                  0.09
                      Sorts:                 10.32                  0.44
                     Logons:                  0.10                  0.00
                   Executes:              1,624.75                 68.85
               Transactions:                 23.60  % Blocks changed per Read:   10.48    Recursive Call %:    98.17
 Rollback per transaction %:    4.31       Rows per Sort:   132.06Instance Efficiency Percentages (Target 100%)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            Buffer Nowait %:  100.00       Redo NoWait %:  100.00
            Buffer  Hit   %:   97.29    In-memory Sort %:  100.00
            Library Hit   %:   99.69        Soft Parse %:   95.03
         Execute to Parse %:   97.51         Latch Hit %:   99.94
Parse CPU to Parse Elapsd %:   70.23     % Non-Parse CPU:   99.52Instance Activity Stats             DB/Inst: BILLBJ/billbj2  Snaps: 7839-7840Statistic                                     Total     per Second     per Trans
-------------------------------- ------------------ -------------- -------------
recursive calls                           7,870,945        2,166.7          91.8
recursive cpu usage                         263,142           72.4           3.1

Answer 1

statspack 没用过。 好用吗？

Answer 2

有些sql语句的执行过程中，并不是单纯的只是对这个sql的简单执行，有时解析会用到数据字典，或者是有时会更新数据字典的信息，这些执行都是有你的sql执行所连带派生出来的，也就被称之为recursive calls。在sql trace里可以看到这些recursive calls。