weblogic连接池配置_weblogic连接scan ip_weblogic长连接(3)

原来是UNDO表空间。那么另一个疑问就会来了，为什么在UNDO上产生了如此之多的单块读？首先要肯定的是，这条简单的查询语句，是进行的一致性读。那么在进行一致性读的过程中，会有两个动作会涉及到读UNDO块，延迟块清除和构建CR块。下面我们用另一个脚本来查看会话当时的状况：

SQL> @snapper all,out 5 3 4038  
Sampling SID 4038 with interval 5 seconds, taking 3 snapshots...
setting stats to all due option = all

-- Session Snapper v3.52 by Tanel Poder @ E2SN ( http://tech.e2sn.com )

-------------------------------------------------------------------------------------------------------------------------------------
    SID, USERNAME  , TYPE, STATISTIC                                                 ,     HDELTA, HDELTA/SEC,    %TIME, GRAPH
-------------------------------------------------------------------------------------------------------------------------------------
   4038, BILL_MY   , STAT, session logical reads                                     ,        488,       97.6,
   4038, BILL_MY   , STAT, user I/O wait time                                        ,        429,       85.8,
   4038, BILL_MY   , STAT, non - idle wait time                                      ,        429,       85.8,
   4038, BILL_MY   , STAT, non - idle wait count                                     ,        377,       75.4,
   4038, BILL_MY   , STAT, physical read total IO requests                           ,        377,       75.4,
   4038, BILL_MY   , STAT, physical read total bytes                                 ,      3.13M,    625.87k,
   4038, BILL_MY   , STAT, cell physical IO interconnect bytes                       ,      3.13M,    625.87k,
   4038, BILL_MY   , STAT, consistent gets                                           ,        488,       97.6,
   4038, BILL_MY   , STAT, consistent gets from cache                                ,        488,       97.6,
   4038, BILL_MY   , STAT, consistent gets from cache (fastpath)                     ,          8,        1.6,
   4038, BILL_MY   , STAT, consistent gets - examination                             ,        478,       95.6,
   4038, BILL_MY   , STAT, logical read bytes from cache                             ,         4M,    799.54k,
   4038, BILL_MY   , STAT, physical reads                                            ,        382,       76.4
   4038, BILL_MY   , STAT, physical reads cache                                      ,        382,       76.4,
   4038, BILL_MY   , STAT, physical read IO requests                                 ,        377,       75.4,
   4038, BILL_MY   , STAT, physical read bytes                                       ,      3.13M,    625.87k,
   4038, BILL_MY   , STAT, db block changes                                          ,          9,        1.8,
   4038, BILL_MY   , STAT, consistent changes                                        ,        469,       93.8,
   4038, BILL_MY   , STAT, free buffer requested                                     ,        392,       78.4,
   4038, BILL_MY   , STAT, CR blocks created                                         ,         10,          2,
   4038, BILL_MY   , STAT, physical reads cache prefetch                             ,          5,          1,
   4038, BILL_MY   , STAT, shared hash latch upgrades - no wait                      ,        375,         75,
   4038, BILL_MY   , STAT, calls to kcmgas                                           ,        376,       75.2,
   4038, BILL_MY   , STAT, redo entries                                              ,          9,        1.8,
   4038, BILL_MY   , STAT, redo size                                                 ,        648,      129.6,
   4038, BILL_MY   , STAT, redo subscn max counts                                    ,          9,        1.8,
   4038, BILL_MY   , STAT, file io wait time                                         ,       4.3M,    860.97k,
   4038, BILL_MY   , STAT, data blocks consistent reads - undo records applied       ,        476,       95.2,
   4038, BILL_MY   , STAT, rollbacks only - consistent read gets                     ,          1,         .2,
   4038, BILL_MY   , STAT, cleanouts and rollbacks - consistent read gets            ,          9,        1.8,
   4038, BILL_MY   , STAT, immediate (CR) block cleanout applications                ,          9,        1.8,
   4038, BILL_MY   , STAT, commit txn count during cleanout                          ,          9,        1.8,
   4038, BILL_MY   , STAT, cleanout - number of ktugct calls                         ,          9,        1.8,
   4038, BILL_MY   , STAT, table scan rows gotten                                    ,        492,       98.4,
   4038, BILL_MY   , STAT, table scan blocks gotten                                  ,         10,          2,
   4038, BILL_MY   , STAT, heap block compress                                       ,         72,       14.4,
   4038, BILL_MY   , TIME, DB CPU                                                    ,    60.99ms,     12.2ms,     1.2%, |@         |
   4038, BILL_MY   , TIME, sql execute elapsed time                                  ,      4.35s,   869.12ms,    86.9%, |@@@@@@@@@ |
   4038, BILL_MY   , TIME, DB time                                                   ,      4.35s,   869.12ms,    86.9%, |@@@@@@@@@ |
   4038, BILL_MY   , WAIT, db file sequential read                                   ,      4.17s,   834.69ms,    83.5%, |@@@@@@@@@ |
   4038, BILL_MY   , WAIT, db file scattered read                                    ,    49.17ms,     9.83ms,     1.0%, |@         |
--  End of Stats snap 1, end=2012-05-21 22:22:16, seconds=5
...省略另两次的采样输出。

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