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read by other session等待事件

Oracle 作者：shuyingxi 时间：2014-07-30 17:30:10 0 删除 编辑


转自 http://blog.csdn.net/hrich/article/details/8564141

今天处理客户数据库问题的时候，发现该数据库有大量的read by other session等待事件，借此记录下。

首先根据文档，这个事件的解释如下：


When informationis requested from the database, Oracle will first read the data from disk intothe database buffer cache. If two or more sessions request the sameinformation, the first session will read the data into the buffer cache whileother sessions wait. In previous versions this wait was classified under the"buffer busy waits" event. However, in Oracle 10.1 and higher thiswait time is now broken out into the "read by other session" waitevent. Excessive waits for this event are typically due to several processesrepeatedly reading the same blocks, e.g. many sessions scanning the same indexor performing full table scans on the same table. Tuning this issue is a matterof finding and eliminating this contention.


       当请求一个数据时，如果buffer cache没有该数据时，Oracle会从磁盘将数据读入buffer cache。

       如果有两个或者多个session 请求相同的信息，那么第一个session 会将这个信息读入buffer cache，其他的session 就会出现等待。 

       在10.1之前，该等待事件归类为bufferbusy waits，在Oracle 10.1之后，单独将该事件拿出并命令为read by other session。

  一般来说出现这种等待事件是因为多个进程重复的读取相同的blocks，比如一些session 扫描相同的index或者在相同的block上执行full table scan。

      解决这个等待事件最好是找到并优化相关的SQL语句。

       read by other session 等待的出现也说明数据库存在热块问题，所以该等待事件通常会有db file sequential read或db file scattered read 同时出现。


来看看今天遇到的情况：

在查看数据库等待事件的时候，发现有大量的read other session和db file scattered read事件


点击(此处)折叠或打开

  1. select sid,
  2. serial#,
  3. username,
  4. status,
  5. machine,
  6. program,
  7. sql_hash_value,
  8. sql_id,
  9. to_char(logon_time,\'yyyy-mm-dd hh24:mi:ss\'),
  10. event,
  11. p1,
  12. p2
  13. from v$session
  14. where event in (\'read by other session\', \'db file scattered read\');
  16. SID SERIAL# USERNAME STATUS MACHINE PROGRAM SQL_HASH_VALUE SQL_ID TO_CHAR(LOGON_TIME,\'YYYY-MM-DD EVENT P1 P2
  17. ---------- ---------- ----------- -------- --------------- ----------------------------- -------------- ------------- ------------------------------ ----------------------------- ---------- ----------
  18. 347 822 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:44:20 read by other session 9 103885
  19. 348 1558 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:34:45 read by other session 9 171789
  20. 349 1879 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:17:03 db file scattered read 9 610910
  21. 350 1241 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:46:19 read by other session 9 103885
  22. 351 1067 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:44:50 db file scattered read 9 103885
  23. 352 3296 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:35:19 read by other session 9 171789
  24. 353 391 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:21:49 db file scattered read 9 441841
  25. 354 616 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:23:18 db file scattered read 9 391294
  26. 355 681 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:25:13 read by other session 9 279803
  27. 356 712 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:33:17 read by other session 9 171789
  28. 357 510 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:45:17 read by other session 9 103885
  29. 358 1625 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:30:38 read by other session 9 171789
  30. 359 956 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:20:13 db file scattered read 9 568327
  31. 360 837 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:16:22 db file scattered read 9 624695
  32. 364 10488 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:17:30 db file scattered read 9 590289
  33. 370 3993 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:20:37 db file scattered read 9 451617
  34. 376 3258 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:49:47 db file scattered read 9 69053
  35. 377 4779 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:44:12 read by other session 9 103885
  36. 380 21129 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:15:39 db file scattered read 9 668803
  37. 381 2716 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:34:07 read by other session 9 171789
  38. 385 1617 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:27:59 read by other session 9 171789
  39. 389 1681 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:16:07 db file scattered read 9 643364
  40. 391 6657 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:26:49 db file scattered read 9 234271
  41. 392 43902 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:30:23 read by other session 9 171789
  42. 395 7003 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:15:15 db file scattered read 9 719929
  43. 398 5246 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:33:25 read by other session 9 171789
  44. 399 9635 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:15:39 db file scattered read 9 672689
  45. 410 5588 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:17:05 db file scattered read 9 604003
  46. 412 980 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:31:20 read by other session 9 171789
  47. 415 4591 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:20:13 db file scattered read 9 556541
  48. 416 6649 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:33:33 read by other session 9 171789
  49. 418 21354 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:27:21 db file scattered read 9 183001
  50. 419 43412 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:17:26 db file scattered read 9 592652
  51. 420 3669 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:19:26 db file scattered read 9 581417
  52. 423 2586 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:33:25 read by other session 9 171789
  53. 430 27397 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:31:50 read by other session 9 171789
  54. 432 7621 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:19:39 db file scattered read 9 534361
  55. 435 3845 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:29:16 read by other session 9 171789
  56. 439 3293 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:44:09 read by other session 9 103885
  57. 440 16800 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:43:40 read by other session 9 103885
  58. 446 18697 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:18:18 db file scattered read 9 584413
  59. 451 4734 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:45:40 read by other session 9 103885
  60. 452 2594 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:27:05 db file scattered read 9 210845
  61. 453 9508 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:16:22 db file scattered read 9 615554
  62. 458 6139 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:44:31 read by other session 9 103885
  63. 460 18012 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:44:08 read by other session 9 103885
  64. 461 3224 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:14:26 db file scattered read 9 724229
  65. 465 4371 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:34:18 read by other session 9 171789
  66. 466 4650 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:20:22 read by other session 9 534361
  67. 468 8735 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:25:22 db file scattered read 9 268194
  68. 469 14362 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:27:05 db file scattered read 9 202463
  69. 471 7194 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:44:07 read by other session 9 103885
  70. 474 2533 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:25:37 db file scattered read 9 248817
  71. 478 3757 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:46:43 read by other session 9 103885
  72. 485 4438 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:26:28 db file scattered read 9 236349
  73. 488 7859 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:26:19 read by other session 9 239613
  74. 489 8827 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:45:17 read by other session 9 103885
  75. 491 6996 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:24:16 db file scattered read 9 293921
  76. 492 21059 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:51:42 read by other session 9 69053
  77. 493 7681 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:30:42 read by other session 9 171789
  78. 497 4636 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:28:42 read by other session 9 171789
  79. 500 4062 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:48:06 read by other session 9 103885
  80. 501 9340 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:26:19 db file scattered read 9 239613
  81. 504 9746 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:33:57 read by other session 9 171789
  82. 506 4258 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:17:05 db file scattered read 9 605955
  83. 507 3436 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:17:59 db file scattered read 9 584829
  84. 509 3990 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:15:37 db file scattered read 9 689377
  85. 511 5592 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:48:47 read by other session 9 69053
  86. 515 2380 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:33:11 read by other session 9 171789
  87. 516 5049 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:23:42 db file scattered read 9 375192
  88. 517 11081 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:16:49 read by other session 9 612067
  89. 518 19019 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:19:16 db file scattered read 9 582651
  90. 519 2947 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:44:03 read by other session 9 103885
  91. 520 44555 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:19:39 db file scattered read 9 573202
  92. 523 32606 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:43:40 read by other session 9 103885
  93. 524 14352 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:25:40 read by other session 9 248817
  94. 525 49196 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:33:43 read by other session 9 171789
  95. 526 2815 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:22:03 db file scattered read 9 432421
  96. 527 7558 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:20:40 db file scattered read 9 447233
  97. 528 19934 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:18:42 db file scattered read 9 583660
  98. 532 12000 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:15:23 db file scattered read 9 703321
  99. 535 19291 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:15:40 db file scattered read 9 651921
  100. 537 5808 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:16:28 db file scattered read 9 612067
  101. 539 5824 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:44:08 read by other session 9 103885
  102. 542 22756 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:44:08 read by other session 9 103885
  103. 543 28090 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:21:19 db file scattered read 9 446657
  104. 546 25606 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:21:19 db file scattered read 9 443777
  105. 547 21390 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:31:28 read by other session 9 171789
  106. 548 31131 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:22:59 db file scattered read 9 392686
  107. 557 20900 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:22:05 db file scattered read 9 420589
  108. 558 7787 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:21:28 db file scattered read 9 442321
  109. 560 49814 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:45:14 read by other session 9 103885
  110. 561 33975 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:28:18 read by other session 9 171789
  111. 603 708 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:33:50 read by other session 9 171789
  112. 645 24200 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:22:05 db file scattered read 9 419926
  113. 663 8601 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:23:42 db file scattered read 9 376348
  114. 669 42540 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:44:08 read by other session 9 103885
  115. 670 355 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:31:20 db file scattered read 9 171789
  116. 671 5023 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:33:57 read by other session 9 171789
  117. 676 572 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:14:39 db file scattered read 9 723209
  118. 677 5142 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:16:26 db file scattered read 9 615415
  119. 687 8508 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:15:15 db file scattered read 9 711833
  120. 688 565 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:32:03 read by other session 9 171993
  121. 700 20809 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:25:13 db file scattered read 9 279835
  122. 702 3931 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:33:21 read by other session 9 171993
  123. 705 3521 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:16:00 db file scattered read 9 649425
  124. 772 1005 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:27:21 db file scattered read 9 189930
  125. 797 1081 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:47:35 read by other session 9 104045
  126. 806 4809 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:18:42 read by other session 9 584461
  127. 819 32486 SYH123 ACTIVE LENOVO-EWJS4146 300319264 187mwcn8yd0j0 2013-02-01 11:28:43 read by other session 9 171993
  128. 839 26168 SYH123 ACTIVE LENOVO-EWJS4146 2307979633 bj3rk3a4t1ybj 2013-02-01 11:27:03 db file scattered read 9 232669



进一步查看read other session和db file scattered read事件相关语句的SQL_ID


点击(此处)折叠或打开

  1. SQL> select distinct sql_id
  2.   2 from v$session
  3.   3 where event in (\'read by other session\', \'db file scattered read\');
  4.    
  5. SQL_ID
  6. -------------
  7. bj3rk3a4t1ybj
  8. 187mwcn8yd0j0

发现所有的read other session和db file scattered read事件都集中在上面两个SQL语句上。



在查看read other session的参数情况：


点击(此处)折叠或打开

  1. SQL> select name,parameter1,parameter2,wait_class from v$event_name where name=\'read by other session\';
  2.   
  3. NAME PARAMETER1 PARAMETER2 WAIT_CLASS
  4. ------------------------------ ---------- ---------- --------------------
  5. read by other session file# block# User I/O
  6.   
  7. SQL>

可以看p1代表了file#，p2代表block#


查看这些read other session所访问的对象


点击(此处)折叠或打开

  1. SQL> select t.owner,t.segment_name,t.segment_type from dba_extents t where t.file_id = 9 and 103885 between t.block_id and t.block_id+t.blocks
  2.   2 /
  3.    
  4. OWNER SEGMENT_NAME SEGMENT_TYPE
  5. ------------------------------ ---------------------------------------- ------------------
  6. SCPEND TF_TASK_TASKINFOHISTB TABLE
  7.    
  8. SQL>
  9.   
  10. SQL>
  11. SQL> select t.owner, t.segment_name, t.segment_type
  12.   2 from dba_extents t
  13.   3 where t.file_id = 9
  14.   4 and 69053 between t.block_id and t.block_id + t.blocks;
  15.     
  16.    
  17. OWNER SEGMENT_NAME SEGMENT_TYPE
  18. ------------------------------ ---------------------------------------- ------------------
  19. SCPEND TF_TASK_TASKINFOHISTB TABLE
  20.    
  21. SQL>
  22.   
  23. SQL>
  24. SQL> select t.owner, t.segment_name, t.segment_type
  25.   2 from dba_extents t
  26.   3 where t.file_id = 9
  27.   4 and 590289 between t.block_id and t.block_id + t.blocks;
  28.     
  29.    
  30. OWNER SEGMENT_NAME SEGMENT_TYPE
  31. ------------------------------ ---------------------------------------- ------------------
  32. SCPEND TF_TASK_TASKINFOHISTB TABLE

发现都是访问的同一个表。


再来看看该SQL的执行计划：


可以看到相关SQL确实在对该表做全表扫描的操作，耗时达到22分钟。


后续操作就是对该SQL进行优化


来自 “ ITPUB博客 ” ，链接：https://blog.itpub.net/438414/viewspace-1242639/ ，如需转载，请注明出处，否则将追究法律责任。

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