Oracle事务原理探究2--读书笔记五

续上篇...

3. ?数据块访问与undo

? ? ? ? 任何时候当会话查看一个数据块的时候，都需要保证看到的是适当的数据版本。从外部观点来看，这意味着会话不应该看到任何未提交的数据，或许还不应该看到查询开始后修改并提交的数据（取决于事务的隔离级别），这称为数据的读一致性版本。

? ? ? ? 下面我们来谈谈oracle怎么实现读一致性版本的：

3.1 设置场景

? ? ? ? 我们会创建一张表，里面插入3条数据，然后开几个会话对其进行操作

3.1.1 连接oracle，以任何一个用户登录即可，初始化一些格式

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1. execute?dbms_random.seed(0)??
2. ??
3. set?doc?off??
4. doc??
5. ??
6. end?doc?is?marked?with?#??
7. ??
8. #??
9. ??
10. set?linesize?120??
11. set?trimspool?on??
12. set?pagesize?24??
13. set?arraysize?25??
14. ??
15. --?set?longchunksize?32768??
16. --?set?long?32768??
17. ??
18. set?autotrace?off??
19. ??
20. clear?breaks??
21. ttitle?off??
22. btitle?off??
23. ??
24. column?owner?format?a15??
25. column?segment_name?format?a20??
26. column?table_name?format?a20??
27. column?index_name?format?a20??
28. column?object_name?format?a20??
29. column?subobject_name?format?a20??
30. column?partition_name?format?a20??
31. column?subpartition_name?format?a20??
32. column?column_name?format?a20??
33. column?column_expression?format?a40?word?wrap??
34. column?constraint_name?format?a20??
35. ??
36. column?referenced_name?format?a30??
37. ??
38. column?file_name?format?a60??
39. ??
40. column?low_value?format?a24??
41. column?high_value?format?a24??
42. ??
43. column?parent_id_plus_exp???format?999??
44. column?id_plus_exp??????format?990??
45. column?plan_plus_exp????????format?a90??
46. column?object_node_plus_exp?format?a14??
47. column?other_plus_exp???????format?a90??
48. column?other_tag_plus_exp???format?a29??
49. ??
50. column?access_predicates????format?a80??
51. column?filter_predicates????format?a80??
52. column?projection???????format?a80??
53. column?remarks??????????format?a80??
54. column?partition_start??????format?a12??
55. column?partition_stop???????format?a12??
56. column?partition_id?????format?999??
57. column?other_tag????????format?a32??
58. column?object_alias?????format?a24??
59. ??
60. column?object_node??????format?a13??
61. column??other???????????format?a150??
62. ??
63. column?os_username??????format?a30??
64. column?terminal?????????format?a24??
65. column?userhost?????????format?a24??
66. column?client_id????????format?a24??
67. ??
68. column?statistic_name?format?a35??
69. ??
70. column?namespace?format?a20??
71. column?attribute?format?a20??
72. ??
73. column?hint?format?a40??
74. ??
75. column?start_time???format?a25??
76. column?end_time?????format?a25??
77. ??
78. column?time_now?noprint?new_value?m_timestamp??
79. ??
80. set?feedback?off??
81. ??
82. select?to_char(sysdate,‘hh24miss‘)?time_now?from?dual;??
83. commit;??
84. ??
85. set?feedback?on??
86. ??
87. set?timing?off??
88. set?verify?off??
89. ??
90. alter?session?set?optimizer_mode?=?all_rows;??
91. ??
92. spool?log??

3.1.2 创建表

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1. drop?table?t1;??
2. ??
3. create?table?t1(id?number,?n1?number);??
4. ??
5. insert?into?t1?values(1,1);??
6. insert?into?t1?values(2,2);??
7. insert?into?t1?values(3,3);??
8. ??
9. commit;??
10. ??
11. create?unique?index?t1_i1?on?t1(id);??
12. ??
13. begin??
14. ????dbms_stats.gather_table_stats(??
15. ????????ownname??????=>?user,??
16. ????????tabname??????=>‘T1‘,??
17. ????????estimate_percent?=>?100,??
18. ????????method_opt???=>?‘for?all?columns?size?1‘??
19. ????);??
20. end;??
21. /??
22. ??
23. --??
24. --<span?style="white-space:pre">??</span>For?11g?-?force?to?disc?for?the?dump??
25. --??
26. ??
27. ??
28. alter?system?checkpoint;??

3.1.3 创建一个存储过程，用来转储一个表使用的第一个数据块。

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1. create?or?replace?procedure?dump_table_block(??
2. ????i_tab_name??????in??varchar2,??
3. ????i_owner?????????in??varchar2????default?sys_context(‘userenv‘,‘session_user‘)??
4. )??
5. as??
6. ????m_file_id???number;??
7. ????m_block?????number;??
8. ????m_process???varchar2(32);??
9. ??
10. begin??
11. ??
12. ????execute?immediate??
13. ????????‘?select?‘?||??
14. ????????????‘?dbms_rowid.rowid_relative_fno(rowid),?‘?||??
15. ????????????‘?dbms_rowid.rowid_block_number(rowid)??‘?||??
16. ????????‘?from?‘?||??
17. ????????????i_owner?||???
18. ????????????‘.‘?||??
19. ????????????i_tab_name?||??
20. ????????‘?where?‘?||??
21. ????????????‘?rownum?=?1?‘??
22. ????????into??
23. ????????????m_file_id,?m_block??
24. ????;??
25. ??
26. ????execute?immediate??
27. ????????‘alter?system?dump?datafile?‘?||?m_file_id?||??
28. ????????‘?block?‘?||?m_block??
29. ????;??
30. ??
31. --??
32. --??For?non-MTS,?work?out?the?trace?file?name??
33. --??
34. ??
35. ????select??
36. ????????spid??
37. ????into??
38. ????????m_process??
39. ????from??
40. ????????v$session???se,??
41. ????????v$process???pr??
42. ????where??
43. --??
44. --??????The?first?option?is?the?9.2?version?for?checking?the?SID??
45. --??????The?second?is?a?quick?and?dirty?option?for?8.1.7??
46. --??????provided?SYS?has?made?v$mystat?visible?(or?this?is?the?sys?account)??
47. --??
48. --??????se.sid?=?(select?dbms_support.mysid?from?dual)??
49. ????????se.sid?=?(select?sid?from?v$mystat?where?rownum?=?1)??
50. ????and?pr.addr?=?se.paddr??
51. ????;??
52. ??
53. ????dbms_output.new_line;??
54. ????dbms_output.put_line(‘Trace?file?name?includes:?‘?||?m_process);??
55. ????dbms_output.new_line;??
56. ??
57. exception??
58. ????when?others?then??
59. ????????dbms_output.new_line;??
60. ????????dbms_output.put_line(‘Unspecified?error.‘);??
61. ????????dbms_output.put_line(‘Check?syntax.‘);??
62. ????????dbms_output.put_line(‘dump_table_block({table_name},[{owner}]‘);??
63. ????????dbms_output.new_line;??
64. ????????raise;??
65. end;??
66. .??
67. /??
68. ??
69. show?errors??
70. ??
71. drop?public?synonym?dump_table_block;??
72. create?public?synonym?dump_table_block?for?dump_table_block;??
73. grant?execute?on?dump_table_block?to?public;??

3.1.4 转储表t1的第一个数据块

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1. execute?dump_table_block(‘t1‘)??

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3.1.5 我们会看到：Trace file name includes: 4292这样的字样，到oracle 的trace目录找到这个跟踪文件，我的电脑入戏所示：

E:\app\Administrator\diag\rdbms\orcl\orcl\trace\orcl_ora_4292.trc, ?双击用记事本打开，可以看到如下内容：

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1. Block?header?dump:??0x00416169??
2. ?Object?id?on?Block??Y??
3. ?seg/obj:?0x12e7a??csc:?0x00.326fb7??itc:?2??flg:?O??typ:?1?-?DATA??
4. ?????fsl:?0??fnx:?0x0?ver:?0x01??
5. ???
6. ?Itl???????????Xid??????????????????Uba?????????Flag??Lck????????Scn/Fsc??
7. 0x01???0x0002.005.000005f5??0x00c00b18.0121.0d??--U-????3??fsc?0x0000.00326fb8??
8. 0x02???0x0000.000.00000000??0x00000000.0000.00??----????0??fsc?0x0000.00000000??
9. bdba:?0x00416169??
10. data_block_dump,data?header?at?0x1e256e5c??
11. ===============??
12. tsiz:?0x1fa0??
13. hsiz:?0x18??
14. pbl:?0x1e256e5c??
15. ?????76543210??
16. flag=--------??
17. ntab=1??
18. nrow=3??
19. frre=-1??
20. fsbo=0x18??
21. fseo=0x1f85??
22. avsp=0x1f6d??
23. tosp=0x1f6d??
24. 0xe:pti[0]??nrow=3??offs=0??
25. 0x12:pri[0]?offs=0x1f97??
26. 0x14:pri[1]?offs=0x1f8e??
27. 0x16:pri[2]?offs=0x1f85??
28. block_row_dump:??
29. tab?0,?row?0,?@0x1f97??
30. tl:?9?fb:?--H-FL--?lb:?0x1??cc:?2??
31. col??0:?[?2]??c1?02??
32. col??1:?[?2]??c1?02??
33. tab?0,?row?1,?@0x1f8e??
34. tl:?9?fb:?--H-FL--?lb:?0x1??cc:?2??
35. col??0:?[?2]??c1?03??
36. col??1:?[?2]??c1?03??
37. tab?0,?row?2,?@0x1f85??
38. tl:?9?fb:?--H-FL--?lb:?0x1??cc:?2??
39. col??0:?[?2]??c1?04??
40. col??1:?[?2]??c1?04??
41. end_of_block_dump??
42. End?dump?data?blocks?tsn:?0?file#:?1?minblk?90473?maxblk?90473??
43. Start?dump?data?blocks?tsn:?0?file#:1?minblk?90473?maxblk?90473??

3.2 事务列表
? ? ? ? 这一节，简要介绍一下转储出来的数据块中事务槽的信息，上面数据块的事务槽如下：

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1. ?Itl???????????Xid??????????????????Uba?????????Flag??Lck????????Scn/Fsc??
2. 0x01???0x0002.005.000005f5??0x00c00b18.0121.0d??--U-????3??fsc?0x0000.00326fb8??
3. 0x02???0x0000.000.00000000??0x00000000.0000.00??----????0??fsc?0x0000.00000000??

Itl：列表的数组索引，该值未真正存储在数据块中，它由执行转储的代码生成。该值用在行的锁字节(lb:)中以显示哪个事务锁住了该行。

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Xid: 最近更改该块的事务的事务id，格式是undo段.undo槽.undo序列号.

Uba: undo记录地址，是事务为该块最近生成的undo记录所在块的序列号。

Flag: 标识事务当前状态

? ? ? ? ? ---- ?活动（当Xid中每一个字段为0时表示，无事务）

? ? ? ? ? --U- 上界提交（表明这个事务已经提交，只是还没有清除一些标记）

? ? ? ? ?C---： 已提交并清除（所有标记已清除，比如相关的锁字节都被置0了）

?Lck：块中由该事务锁住的行数

Scn/Fsc：表示提交SCN或者快速提交SCN。

? ? ? ?在我们这个例子中，占用了一个事务槽，flag是--U-表明，事务已经快速提交，但是Lck为3，表明还没有清除锁标记，快速提交的scn是326fb8. Uba指向了最后一条插入的undo记录，这条undo记录会指向上一条插入的undo记录，上一条undo记录指向了上上条插入的undo记录。这样，如果事务失败，或者人工回滚，沿着这条undo链重做就好了。在oracle10g之后，一个数据块的事务槽被硬性规定为169个。（8KB大小的情况下）

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3.3 并发操作

我们需要开启4个事务，如下所示：

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1. session1:?update?t1?set?n1=101??where?id?=?1;??
2. session2:?update?t1?set?n1=102?where?id?=?2;??
3. ??????????????????commit;alter?system?checkpoint;??
4. My?session:?set?transaction?read?only;??
5. session3:?update?t1?set?n1=99?where?id?=?3;?commit;?alter?system?checkpoint;??
6. My?session:?select?id,?n1?from?t1;??

我们在自己的会话查询之前，转储一下数据块的结果，不过转储之前执行一下切换检查点命令（alter system checkpoint;），使改变刷新输出到磁盘。

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1. Itl???????????Xid??????????????????Uba?????????Flag??Lck????????Scn/Fsc??
2. 0x01???0x0009.010.0000062d??0x00c00712.0127.07??--U-????1??fsc?0x0000.0034a241?--flag?U?代表上界提交，意思是这个事务已经提交，只是目前标记还没清理。??
3. 0x02???0x0005.018.0000062a??0x00c0068a.013f.2f??----????1??fsc?0x0000.00000000?----锁住的是id为1的行，为会话1所锁住的行??
4. ??
5. bdba:?0x00416169??
6. data_block_dump,data?header?at?0x1cd0825c??
7. ===============??
8. tsiz:?0x1fa0??
9. hsiz:?0x18??
10. pbl:?0x1cd0825c??
11. ?????76543210??
12. flag=--------??
13. ntab=1??
14. nrow=3??
15. frre=-1??
16. fsbo=0x18??
17. fseo=0x1f71??
18. avsp=0x1f6b??
19. tosp=0x1f6b??
20. ??
21. block_row_dump:??
22. tab?0,?row?0,?@0x1f7b??
23. tl:?10?fb:?--H-FL--?lb:?0x2??cc:?2?--?事务0x2似乎锁住了这一行，其实是锁住了这一行??
24. col??0:?[?2]??c1?02??
25. col??1:?[?3]??c2?02?02??
26. tab?0,?row?1,?@0x1f71??
27. tl:?10?fb:?--H-FL--?lb:?0x0??cc:?2??
28. col??0:?[?2]??c1?03??
29. col??1:?[?3]??c2?02?03??
30. tab?0,?row?2,?@0x1f85??
31. tl:?9?fb:?--H-FL--?lb:?0x1??cc:?2?--?事务0x1似乎锁住了这一行，其实没有锁住，只是锁标记没有清除??
32. col??0:?[?2]??c1?04??
33. col??1:?[?2]??c1?64??
34. end_of_block_dump??

?执行查询之后，转储数据块结果(需要先执行alter system checkpoint;)

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1. Itl???????????Xid??????????????????Uba?????????Flag??Lck????????Scn/Fsc??
2. 0x01???0x0009.010.0000062d??0x00c00712.0127.07??C---????0??scn?0x0000.0034a241?--?flag?C?已提交并清除完成，表明，查询会将已提交的数据清除标记。??
3. 0x02???0x0005.018.0000062a??0x00c0068a.013f.2f??----????1??fsc?0x0000.00000000?---?锁住的是id为1的行，为会话1所锁住的行??
4. bdba:?0x00416169??
5. data_block_dump,data?header?at?0x1cd0825c??
6. ===============??
7. tsiz:?0x1fa0??
8. hsiz:?0x18??
9. pbl:?0x1cd0825c??
10. ?????76543210??
11. flag=--------??
12. ntab=1??
13. nrow=3??
14. frre=-1??
15. fsbo=0x18??
16. fseo=0x1f71??
17. avsp=0x1f6b??
18. tosp=0x1f6b??
19. ??
20. block_row_dump:??
21. tab?0,?row?0,?@0x1f7b??
22. tl:?10?fb:?--H-FL--?lb:?0x2??cc:?2?--?事务0x2似乎锁住了这一行，其实是锁住了这一行。??
23. col??0:?[?2]??c1?02??
24. col??1:?[?3]??c2?02?02??
25. tab?0,?row?1,?@0x1f71??
26. tl:?10?fb:?--H-FL--?lb:?0x0??cc:?2??
27. col??0:?[?2]??c1?03??
28. col??1:?[?3]??c2?02?03??
29. tab?0,?row?2,?@0x1f85??
30. tl:?9?fb:?--H-FL--?lb:?0x0??cc:?2?--锁标记已经被清除了。??
31. col??0:?[?2]??c1?04??
32. col??1:?[?2]??c1?64??
33. end_of_block_dump??

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3.4 真实的查询操作

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? ? ? ?我们知道，如果我们需要查询一个数据，假设我们是事务1，开始于1:00，于1:05分开始查找A表记录1号。另一个事务2于1:01开始，在1:05分之前将A表记录1号修改了3遍，比如最开始记录1号的值是1，另一个事务将其由1改成2，又改成了3，最后改成了4。另一个事务2于1:10提交的。这样我们的事务1查找的记录1号的值应该为1，但是数据块里面的值已经被修改好几遍了，而且已经变成了4。那么oracle是怎么找到原始值1的呢。下面让我们通过一个小例子来解释这种现象：

? ? ? ?其实，就是讲前面的步骤在执行一下，原谅我直接将上面的命令再拷贝一部分放在下面

3.4.1 准备工作

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1. </pre><pre?code_snippet_id="571760"?snippet_file_name="blog_20150104_10_4627320"?name="code"?class="sql">execute?dbms_random.seed(0)??
2. ??
3. set?doc?off??
4. doc??
5. ??
6. end?doc?is?marked?with?#??
7. ??
8. #??
9. ??
10. set?linesize?120??
11. set?trimspool?on??
12. set?pagesize?24??
13. set?arraysize?25??
14. ??
15. --?set?longchunksize?32768??
16. --?set?long?32768??
17. ??
18. set?autotrace?off??
19. ??
20. clear?breaks??
21. ttitle?off??
22. btitle?off??
23. ??
24. column?owner?format?a15??
25. column?segment_name?format?a20??
26. column?table_name?format?a20??
27. column?index_name?format?a20??
28. column?object_name?format?a20??
29. column?subobject_name?format?a20??
30. column?partition_name?format?a20??
31. column?subpartition_name?format?a20??
32. column?column_name?format?a20??
33. column?column_expression?format?a40?word?wrap??
34. column?constraint_name?format?a20??
35. ??
36. column?referenced_name?format?a30??
37. ??
38. column?file_name?format?a60??
39. ??
40. column?low_value?format?a24??
41. column?high_value?format?a24??
42. ??
43. column?parent_id_plus_exp???format?999??
44. column?id_plus_exp??????format?990??
45. column?plan_plus_exp????????format?a90??
46. column?object_node_plus_exp?format?a14??
47. column?other_plus_exp???????format?a90??
48. column?other_tag_plus_exp???format?a29??
49. ??
50. column?access_predicates????format?a80??
51. column?filter_predicates????format?a80??
52. column?projection???????format?a80??
53. column?remarks??????????format?a80??
54. column?partition_start??????format?a12??
55. column?partition_stop???????format?a12??
56. column?partition_id?????format?999??
57. column?other_tag????????format?a32??
58. column?object_alias?????format?a24??
59. ??
60. column?object_node??????format?a13??
61. column??other???????????format?a150??
62. ??
63. column?os_username??????format?a30??
64. column?terminal?????????format?a24??
65. column?userhost?????????format?a24??
66. column?client_id????????format?a24??
67. ??
68. column?statistic_name?format?a35??
69. ??
70. column?namespace?format?a20??
71. column?attribute?format?a20??
72. ??
73. column?hint?format?a40??
74. ??
75. column?start_time???format?a25??
76. column?end_time?????format?a25??
77. ??
78. column?time_now?noprint?new_value?m_timestamp??
79. ??
80. set?feedback?off??
81. ??
82. select?to_char(sysdate,‘hh24miss‘)?time_now?from?dual;??
83. commit;??
84. ??
85. set?feedback?on??
86. ??
87. set?timing?off??
88. set?verify?off??
89. ??
90. alter?session?set?optimizer_mode?=?all_rows;??
91. ??
92. spool?log??
93. --?创建表??
94. drop?table?t1;??
95. ??
96. create?table?t1(id?number,?n1?number);??
97. ??
98. insert?into?t1?values(1,1);??
99. insert?into?t1?values(2,2);??
100. insert?into?t1?values(3,3);??
101. ??
102. commit;??
103. ??
104. create?unique?index?t1_i1?on?t1(id);??
105. ??
106. begin??
107. ????dbms_stats.gather_table_stats(??
108. ????????ownname??????=>?user,??
109. ????????tabname??????=>‘T1‘,??
110. ????????estimate_percent?=>?100,??
111. ????????method_opt???=>?‘for?all?columns?size?1‘??
112. ????);??
113. end;??
114. /??
115. ??
116. --??
117. --<span?style="white-space:pre">??</span>For?11g?-?force?to?disc?for?the?dump??
118. --??
119. ??
120. ??
121. alter?system?checkpoint;??
122. --?创建一个存储过程，用来转储一个表使用的第一个数据块。??
123. create?or?replace?procedure?dump_table_block(??
124. ????i_tab_name??????in??varchar2,??
125. ????i_owner?????????in??varchar2????default?sys_context(‘userenv‘,‘session_user‘)??
126. )??
127. as??
128. ????m_file_id???number;??
129. ????m_block?????number;??
130. ????m_process???varchar2(32);??
131. ??
132. begin??
133. ??
134. ????execute?immediate??
135. ????????‘?select?‘?||??
136. ????????????‘?dbms_rowid.rowid_relative_fno(rowid),?‘?||??
137. ????????????‘?dbms_rowid.rowid_block_number(rowid)??‘?||??
138. ????????‘?from?‘?||??
139. ????????????i_owner?||???
140. ????????????‘.‘?||??
141. ????????????i_tab_name?||??
142. ????????‘?where?‘?||??
143. ????????????‘?rownum?=?1?‘??
144. ????????into??
145. ????????????m_file_id,?m_block??
146. ????;??
147. ??
148. ????execute?immediate??
149. ????????‘alter?system?dump?datafile?‘?||?m_file_id?||??
150. ????????‘?block?‘?||?m_block??
151. ????;??
152. ??
153. --??
154. --??For?non-MTS,?work?out?the?trace?file?name??
155. --??
156. ??
157. ????select??
158. ????????spid??
159. ????into??
160. ????????m_process??
161. ????from??
162. ????????v$session???se,??
163. ????????v$process???pr??
164. ????where??
165. --??
166. --??????The?first?option?is?the?9.2?version?for?checking?the?SID??
167. --??????The?second?is?a?quick?and?dirty?option?for?8.1.7??
168. --??????provided?SYS?has?made?v$mystat?visible?(or?this?is?the?sys?account)??
169. --??
170. --??????se.sid?=?(select?dbms_support.mysid?from?dual)??
171. ????????se.sid?=?(select?sid?from?v$mystat?where?rownum?=?1)??
172. ????and?pr.addr?=?se.paddr??
173. ????;??
174. ??
175. ????dbms_output.new_line;??
176. ????dbms_output.put_line(‘Trace?file?name?includes:?‘?||?m_process);??
177. ????dbms_output.new_line;??
178. ??
179. exception??
180. ????when?others?then??
181. ????????dbms_output.new_line;??
182. ????????dbms_output.put_line(‘Unspecified?error.‘);??
183. ????????dbms_output.put_line(‘Check?syntax.‘);??
184. ????????dbms_output.put_line(‘dump_table_block({table_name},[{owner}]‘);??
185. ????????dbms_output.new_line;??
186. ????????raise;??
187. end;??
188. .??
189. /??
190. ??
191. show?errors??
192. ??
193. drop?public?synonym?dump_table_block;??
194. create?public?synonym?dump_table_block?for?dump_table_block;??
195. grant?execute?on?dump_table_block?to?public;??

?

?

创建一个转储undo块的存储过程

?

[sql]?view plaincopy

?

1. create?or?replace?procedure?dump_undo_block??
2. as??
3. ????m_xidusn????????number;??
4. ????m_header_file_id????number;??
5. ????m_header_block_id???number;??
6. ????m_start_file_id?????number;??
7. ????m_start_block_id????number;??
8. ????m_file_id???????number;??
9. ????m_block_id??????number;??
10. ????m_process???????number;??
11. begin??
12. ??
13. ????select??
14. ????????xidusn,??
15. ????????start_ubafil,??
16. ????????start_ubablk,??
17. ????????ubafil,???
18. ????????ubablk??
19. ????into??
20. ????????m_xidusn,??
21. ????????m_start_file_id,??
22. ????????m_start_block_id,??
23. ????????m_file_id,??
24. ????????m_block_id??
25. ????from??
26. ????????v$session???ses,??
27. ????????v$transaction???trx??
28. ????where??
29. ????????ses.sid?=?(select?mys.sid?from?V$mystat?mys?where?rownum?=?1)??
30. ????and?trx.ses_addr?=?ses.saddr??
31. ????;??
32. ??
33. ????select???
34. ????????file_id,?block_id???
35. ????into??
36. ????????m_header_file_id,??
37. ????????m_header_block_id??
38. ????from???
39. ????????dba_rollback_segs???
40. ????where???
41. ????????segment_id?=?m_xidusn??
42. ????;??
43. ??
44. ??
45. ????dbms_output.put_line(‘Header??File:?‘?||?m_header_file_id?||?‘?Header?block:?‘??||?m_header_block_id);??
46. ????dbms_output.put_line(‘Start???File:?‘?||?m_start_file_id??||?‘?Start?block:?‘???||?m_start_block_id);??
47. ????dbms_output.put_line(‘Current?File:?‘?||?m_file_id????????||?‘?Current?block:?‘?||?m_block_id);??
48. ??
49. ??
50. ????dbms_system.ksdwrt(1,‘===================‘);??
51. ????dbms_system.ksdwrt(1,‘Undo?Segment?Header‘);??
52. ????dbms_system.ksdwrt(1,‘===================‘);??
53. ??
54. ????execute?immediate??
55. ????????‘alter?system?dump?datafile?‘?||?m_header_file_id?||‘?block?‘?||?m_header_block_id;??
56. ??
57. ????dbms_system.ksdwrt(1,‘================‘);??
58. ????dbms_system.ksdwrt(1,‘Undo?Start?block‘);??
59. ????dbms_system.ksdwrt(1,‘================‘);??
60. ??
61. ????execute?immediate??
62. ????????‘alter?system?dump?datafile?‘?||?m_start_file_id?||‘?block?‘?||?m_start_block_id;??
63. ??
64. ????if?m_start_block_id?!=?m_block_id?then??
65. ??
66. ????????dbms_system.ksdwrt(1,‘==================‘);??
67. ????????dbms_system.ksdwrt(1,‘Current?Undo?block‘);??
68. ????????dbms_system.ksdwrt(1,‘==================‘);??
69. ??
70. ????????execute?immediate??
71. ????????????‘alter?system?dump?datafile?‘?||?m_file_id?||‘?block?‘?||?m_block_id;??
72. ??
73. ????end?if;??
74. ??
75. ????select??
76. ????????spid??
77. ????into??
78. ????????m_process??
79. ????from??
80. ????????v$session???se,??
81. ????????v$process???pr??
82. ????where???se.sid?=?(select?sid?from?v$mystat?where?rownum?=?1)??
83. ????and??
84. ????????pr.addr?=?se.paddr??
85. ????;??
86. ??
87. ????dbms_output.put_line(‘Trace?file?name?includes:?‘?||?m_process);??
88. ??
89. end;??
90. /??
91. ??
92. grant?execute?on?dump_undo_block?to?public;??
93. ??
94. drop???public?synonym?dump_undo_block;???
95. create?public?synonym?dump_undo_block?for?dump_undo_block;??

? ? ? ??

?

以上步骤只是创建了一个表t1，

? ? ? ?3.4.2 转储表t1的第一个数据块

[sql]?view plaincopy

?

1. execute?dump_table_block(‘t1‘)??

?

? ? ? ? 3.4.3 另外开启一个会话，将id为1的记录n1的值改为101，然后改为102，然后改为103。并记录块的变化和undo块的变化。

?

[sql]?view plaincopy

?

1. select?*?from?t1;--清除标记????
2. alter?system?checkpoint;--刷新输出磁盘，执行完等5,6s??
3. execute?dump_table_block(‘t1‘)--转储数据块??<span?style="color:#ff0000;">序号1</span>??
4. update?t1?set?n1=101?where?id=1;--第一次更新??
5. alter?system?checkpoint;--刷新输出磁盘，执行完等5,6s??
6. execute?dump_table_block(‘t1‘)--转储数据块??
7. execute?dump_undo_block--转储undo块??<span?style="color:#ff0000;">序号2</span>??
8. update?t1?set?n1=102?where?id=1;--第二次更新??
9. alter?system?checkpoint;--刷新输出磁盘，执行完等5,6s??
10. execute?dump_table_block(‘t1‘)--转储数据块??
11. execute?dump_undo_block--转储undo块??<span?style="color:#ff0000;">序号3</span>??
12. update?t1?set?n1=103?where?id=1;--第三次更新??
13. alter?system?checkpoint;--刷新输出磁盘，执行完等5,6s??
14. execute?dump_table_block(‘t1‘)--转储数据块??
15. execute?dump_undo_block--转储undo块??<span?style="color:#ff0000;">序号4</span>??

?

? ? ? ?3.4.4 找到转储出来的日志文件

? ? ? ?序号1 执行完后

?

[sql]?view plaincopy

?

1. Itl???????????Xid??????????????????Uba?????????Flag??Lck????????Scn/Fsc??
2. 0x01???0x0003.015.0000065c??0x00c009af.01e8.1c??--U-????3??fsc?0x0000.0035e07c?--理论上，这里的标记应该被清除了??
3. 0x02???0x0000.000.00000000??0x00000000.0000.00??----????0??fsc?0x0000.00000000??
4. bdba:?0x00416169??
5. data_block_dump,data?header?at?0x1ce9705c??

? ? 标记没有清掉，不知道为什么

序号2 执行完后
数据块转储结果

[sql]?view plaincopy

?

1. ***?2015-01-04?22:52:48.506??
2. Start?dump?data?blocks?tsn:?0?file#:1?minblk?90473?maxblk?90473??
3. Block?dump?from?cache:??
4. Dump?of?buffer?cache?at?level?4?for?tsn=0,?rdba=4284777??
5. ??
6. Itl???????????Xid??????????????????Uba?????????Flag??Lck????????Scn/Fsc??
7. 0x01???0x0003.015.0000065c??0x00c009af.01e8.1c??C---????0??scn?0x0000.0035e07c?--标记被清除了??
8. 0x02???0x0004.00b.00000595??0x00c02694.0109.1d??----????1??fsc?0x0000.00000000?--锁住了修改的行??
9. bdba:?0x00416169??
10. data_block_dump,data?header?at?0x1ce9705c??

undo块转储结果

?

?

[sql]?view plaincopy

?

1. ***?2015-01-04?22:53:40.834??
2. ===================??
3. Undo?Segment?Header??
4. ===================??
5. Start?dump?data?blocks?tsn:?2?file#:3?minblk?176?maxblk?176??
6. Block?dump?from?cache:??
7. Dump?of?buffer?cache?at?level?4?for?tsn=2,?rdba=12583088??
8. .....??
9. TRN?TBL::??
10. ???
11. ??index??state?cflags??wrap#????uel?????????scn????????????dba????????????parent-xid????nub?????stmt_num????cmt??
12. ??------------------------------------------------------------------------------------------------??
13. ???0x00????9????0x00??0x0593??0x000c??0x0000.0035df6c??0x00c02693??0x0000.000.00000000??0x00000002???0x00000000??1420382305??
14. ???0x01????9????0x00??0x056d??0x001e??0x0000.0035dcd1??0x00c02692??0x0000.000.00000000??0x00000001???0x00000000??1420381360??
15. ???0x02????9????0x00??0x0591??0x0005??0x0000.0035de9e??0x00c02692??0x0000.000.00000000??0x00000001???0x00000000??1420381960??
16. ???0x03????9????0x00??0x0594??0x0018??0x0000.0035e16f??0x00c02694??0x0000.000.00000000??0x00000001???0x00000000??1420382905??
17. ???0x04????9????0x00??0x0594??0x001f??0x0000.0035e189??0x00c02694??0x0000.000.00000000??0x00000001???0x00000000??1420382905??
18. ???0x05????9????0x00??0x0594??0x0009??0x0000.0035deed??0x00c02692??0x0000.000.00000000??0x00000001???0x00000000??1420382080??
19. ???0x06????9????0x00??0x0594??0x0019??0x0000.0035e080??0x00c02694??0x0000.000.00000000??0x00000001???0x00000000??1420382629??
20. ???0x07????9????0x00??0x0593??0x0002??0x0000.0035de5e??0x00c02692??0x0000.000.00000000??0x00000001???0x00000000??1420381815??
21. ???0x08????9????0x00??0x0594??0x000a??0x0000.0035e089??0x00c02693??0x0000.000.00000000??0x00000001???0x00000000??1420382629??
22. ???0x09????9????0x00??0x0592??0x001d??0x0000.0035df03??0x00c02692??0x0000.000.00000000??0x00000001???0x00000000??1420382080??
23. ???0x0a????9????0x00??0x0593??0x0011??0x0000.0035e0b8??0x00c02694??0x0000.000.00000000??0x00000001???0x00000000??1420382639??
24. ???0x0b???10????0x80??0x0595??0x0003??0x0000.00000000??0x00c02694??0x0000.000.00000000??0x00000001???0x00000000??0?<span?style="color:#ff0000;">--跟数据块的事务槽对上了</span>??
25. ???0x0c????9????0x00??0x0594??0x001c??0x0000.0035dfad??0x00c02693??0x0000.000.00000000??0x00000001???0x00000000??1420382440??
26. ???0x0d????9????0x00??0x0592??0x0014??0x0000.0035ddac??0x00c02692??0x0000.000.00000000??0x00000001???0x00000000??1420381705??
27. ?.....??
28. *-----------------------------??
29. *?Rec?#0x1d??slt:?0x0b??objn:?77560(0x00012ef8)??objd:?77560??tblspc:?0(0x00000000)??
30. *???????Layer:??11?(Row)???opc:?1???rci?0x00?????
31. Undo?type:??Regular?undo????Begin?trans????Last?buffer?split:??No???
32. Temp?Object:??No???
33. Tablespace?Undo:??No???
34. rdba:?0x00000000Ext?idx:?0??
35. flg2:?0??
36. *-----------------------------??
37. uba:?0x00c02694.0109.1c?ctl?max?scn:?0x0000.0035dc32?prv?tx?scn:?0x0000.0035dc72??
38. txn?start?scn:?scn:?0x0000.0035e1d6?logon?user:?0??
39. ?prev?brb:?12592785?prev?bcl:?0??
40. KDO?undo?record:??
41. KTB?Redo???
42. op:?0x03??ver:?0x01????
43. compat?bit:?4?(post-11)?padding:?0??
44. op:?Z??
45. KDO?Op?code:?URP?row?dependencies?Disabled??
46. ??xtype:?XA?flags:?0x00000000??bdba:?0x00416169??hdba:?0x00416168??
47. itli:?2??ispac:?0??maxfr:?4863??
48. tabn:?0?slot:?0(0x0)?flag:?0x2c?lock:?0?ckix:?0??
49. ncol:?2?nnew:?1?size:?-1??
50. col??1:?[?2]??c1?02<span?style="color:#ff0000;">--?这是数据块事务槽uba的地址指向的undo记录，c1?02?代表着1，说明修改前是1.</span>??

?

?

序号3执行完后

数据块转储结果

[sql]?view plaincopy

?

1. ***?2015-01-04?23:06:25.105??
2. Block?dump?from?cache:??
3. Dump?of?buffer?cache?at?level?4?for?tsn=0,?rdba=4284777??
4. .....??
5. Itl???????????Xid??????????????????Uba?????????Flag??Lck????????Scn/Fsc??
6. 0x01???0x0003.015.0000065c??0x00c009af.01e8.1c??C---????0??scn?0x0000.0035e07c??
7. 0x02???0x0004.00b.00000595??0x00c02694.0109.1e??----????1??fsc?0x0000.00000000??--uba?变了，由?0x00c02694.0109.1d?变成了??0x00c02694.0109.1e??
8. </span>bdba:?0x00416169??
9. data_block_dump,data?header?at?0x1ce9705c??
10. .....??
11. block_row_dump:??
12. tab?0,?row?0,?@0x1f7b??
13. tl:?10?fb:?--H-FL--?lb:?0x2??cc:?2??
14. col??0:?[?2]??c1?02??
15. col??1:?[?3]??c2?02?03??
16. tab?0,?row?1,?@0x1f8e??
17. tl:?9?fb:?--H-FL--?lb:?0x0??cc:?2??
18. col??0:?[?2]??c1?03??
19. col??1:?[?2]??c1?03??
20. tab?0,?row?2,?@0x1f85??
21. tl:?9?fb:?--H-FL--?lb:?0x0??cc:?2??
22. col??0:?[?2]??c1?04??
23. col??1:?[?2]??c1?04??
24. end_of_block_dump??

undo块转储结果

[sql]?view plaincopy

?

1. ***?2015-01-04?23:06:31.347??
2. ===================??
3. Undo?Segment?Header??
4. ===================??
5. Start?dump?data?blocks?tsn:?2?file#:3?minblk?176?maxblk?176??
6. Block?dump?from?cache:??
7. Dump?of?buffer?cache?at?level?4?for?tsn=2,?rdba=12583088??
8. ....??
9. ??
10. ??index??state?cflags??wrap#????uel?????????scn????????????dba????????????parent-xid????nub?????stmt_num????cmt??
11. ??------------------------------------------------------------------------------------------------??
12. ???0x00????9????0x00??0x0593??0x000c??0x0000.0035df6c??0x00c02693??0x0000.000.00000000??0x00000002???0x00000000??1420382305??
13. ???0x01????9????0x00??0x056d??0x001e??0x0000.0035dcd1??0x00c02692??0x0000.000.00000000??0x00000001???0x00000000??1420381360??
14. ???0x02????9????0x00??0x0591??0x0005??0x0000.0035de9e??0x00c02692??0x0000.000.00000000??0x00000001???0x00000000??1420381960??
15. ???0x03????9????0x00??0x0594??0x0018??0x0000.0035e16f??0x00c02694??0x0000.000.00000000??0x00000001???0x00000000??1420382905??
16. ???0x04????9????0x00??0x0594??0x001f??0x0000.0035e189??0x00c02694??0x0000.000.00000000??0x00000001???0x00000000??1420382905??
17. ???0x05????9????0x00??0x0594??0x0009??0x0000.0035deed??0x00c02692??0x0000.000.00000000??0x00000001???0x00000000??1420382080??
18. ???0x06????9????0x00??0x0594??0x0019??0x0000.0035e080??0x00c02694??0x0000.000.00000000??0x00000001???0x00000000??1420382629??
19. ???0x07????9????0x00??0x0593??0x0002??0x0000.0035de5e??0x00c02692??0x0000.000.00000000??0x00000001???0x00000000??1420381815??
20. ???0x08????9????0x00??0x0594??0x000a??0x0000.0035e089??0x00c02693??0x0000.000.00000000??0x00000001???0x00000000??1420382629??
21. ???0x09????9????0x00??0x0592??0x001d??0x0000.0035df03??0x00c02692??0x0000.000.00000000??0x00000001???0x00000000??1420382080??
22. ???0x0a????9????0x00??0x0593??0x0011??0x0000.0035e0b8??0x00c02694??0x0000.000.00000000??0x00000001???0x00000000??1420382639??
23. ???0x0b???10????0x80??0x0595??0x0003??0x0000.00000000??0x00c02694??0x0000.000.00000000??0x00000001???0x00000000??0??
24. ???0x0c????9????0x00??0x0594??0x001c??0x0000.0035dfad??0x00c02693??0x0000.000.00000000??0x00000001???0x00000000??1420382440??
25. ???0x0d????9????0x00??0x0592??0x0014??0x0000.0035ddac??0x00c02692??0x0000.000.00000000??0x00000001???0x00000000??1420381705??
26. ?.......??
27. *-----------------------------??
28. *?Rec?#0x1d??slt:?0x0b??objn:?77560(0x00012ef8)??objd:?77560??tblspc:?0(0x00000000)??
29. *???????Layer:??11?(Row)???opc:?1???rci?0x00?????
30. Undo?type:??Regular?undo????Begin?trans????Last?buffer?split:??No???
31. Temp?Object:??No???
32. Tablespace?Undo:??No???
33. rdba:?0x00000000Ext?idx:?0??
34. flg2:?0??
35. *-----------------------------??
36. uba:?0x00c02694.0109.1c?ctl?max?scn:?0x0000.0035dc32?prv?tx?scn:?0x0000.0035dc72??
37. txn?start?scn:?scn:?0x0000.0035e1d6?logon?user:?0??
38. ?prev?brb:?12592785?prev?bcl:?0??
39. KDO?undo?record:??
40. KTB?Redo???
41. op:?0x03??ver:?0x01????
42. compat?bit:?4?(post-11)?padding:?0??
43. op:?Z??
44. KDO?Op?code:?URP?row?dependencies?Disabled??
45. ??xtype:?XA?flags:?0x00000000??bdba:?0x00416169??hdba:?0x00416168??
46. itli:?2??ispac:?0??maxfr:?4863??
47. tabn:?0?slot:?0(0x0)?flag:?0x2c?lock:?0?ckix:?0??
48. ncol:?2?nnew:?1?size:?-1??
49. col??1:?[?2]??c1?02???
50. ???
51. *-----------------------------??
52. *?Rec?#0x1e??slt:?0x0b??objn:?77560(0x00012ef8)??objd:?77560??tblspc:?0(0x00000000)??
53. *???????Layer:??11?(Row)???opc:?1???rci?0x1d?????
54. Undo?type:??Regular?undo???Last?buffer?split:??No???
55. Temp?Object:??No???
56. Tablespace?Undo:??No???
57. rdba:?0x00000000??
58. *-----------------------------??
59. KDO?undo?record:??
60. KTB?Redo???
61. op:?0x02??ver:?0x01????
62. compat?bit:?4?(post-11)?padding:?0??
63. op:?C??uba:?0x00c02694.0109.1d?--指向前一个undo记录??
64. KDO?Op?code:?URP?row?dependencies?Disabled??
65. ??xtype:?XAxtype?KDO_KDOM2?flags:?0x00000080??bdba:?0x00416169??hdba:?0x00416168??
66. itli:?2??ispac:?0??maxfr:?4863??
67. tabn:?0?slot:?0(0x0)?flag:?0x2c?lock:?2?ckix:?0??
68. ncol:?2?nnew:?1?size:?0??
69. Vector?content:???
70. col??1:?[?3]??c2?02?02?--?这是数据块事务槽uba的地址指向的undo记录，c2?02?02?代表着101，说明修改前是101??

?

序号4执行完后

数据块转储结果

[sql]?view plaincopy

?

1. ***?2015-01-04?23:13:22.306??
2. Start?dump?data?blocks?tsn:?0?file#:1?minblk?90473?maxblk?90473??
3. Block?dump?from?cache:??
4. Dump?of?buffer?cache?at?level?4?for?tsn=0,?rdba=4284777??
5. ....??
6. ?Itl???????????Xid??????????????????Uba?????????Flag??Lck????????Scn/Fsc??
7. 0x01???0x0003.015.0000065c??0x00c009af.01e8.1c??C---????0??scn?0x0000.0035e07c??
8. 0x02???0x0004.00b.00000595??0x00c02694.0109.1f??----????1??fsc?0x0000.00000000?--uba?变了，由?0x00c02694.0109.1e?变成了??0x00c02694.0109.1f??
9. bdba:?0x00416169??
10. ....??
11. block_row_dump:??
12. tab?0,?row?0,?@0x1f7b??
13. tl:?10?fb:?--H-FL--?lb:?0x2??cc:?2??
14. col??0:?[?2]??c1?02??
15. col??1:?[?3]??c2?02?04??
16. tab?0,?row?1,?@0x1f8e??
17. tl:?9?fb:?--H-FL--?lb:?0x0??cc:?2??
18. col??0:?[?2]??c1?03??
19. col??1:?[?2]??c1?03??
20. tab?0,?row?2,?@0x1f85??
21. tl:?9?fb:?--H-FL--?lb:?0x0??cc:?2??
22. col??0:?[?2]??c1?04??
23. col??1:?[?2]??c1?04??
24. end_of_block_dump??

undo块转储结果

?

[sql]?view plaincopy

?

1. ***?2015-01-04?23:13:31.622??
2. ===================??
3. Undo?Segment?Header??
4. ===================??
5. Start?dump?data?blocks?tsn:?2?file#:3?minblk?176?maxblk?176??
6. Block?dump?from?cache:??
7. Dump?of?buffer?cache?at?level?4?for?tsn=2,?rdba=12583088??
8. ....??
9. ?index??state?cflags??wrap#????uel?????????scn????????????dba????????????parent-xid????nub?????stmt_num????cmt??
10. ??------------------------------------------------------------------------------------------------??
11. ???0x00????9????0x00??0x0593??0x000c??0x0000.0035df6c??0x00c02693??0x0000.000.00000000??0x00000002???0x00000000??1420382305??
12. ???0x01????9????0x00??0x056d??0x001e??0x0000.0035dcd1??0x00c02692??0x0000.000.00000000??0x00000001???0x00000000??1420381360??
13. ???0x02????9????0x00??0x0591??0x0005??0x0000.0035de9e??0x00c02692??0x0000.000.00000000??0x00000001???0x00000000??1420381960??
14. ???0x03????9????0x00??0x0594??0x0018??0x0000.0035e16f??0x00c02694??0x0000.000.00000000??0x00000001???0x00000000??1420382905??
15. ???0x04????9????0x00??0x0594??0x001f??0x0000.0035e189??0x00c02694??0x0000.000.00000000??0x00000001???0x00000000??1420382905??
16. ???0x05????9????0x00??0x0594??0x0009??0x0000.0035deed??0x00c02692??0x0000.000.00000000??0x00000001???0x00000000??1420382080??
17. ???0x06????9????0x00??0x0594??0x0019??0x0000.0035e080??0x00c02694??0x0000.000.00000000??0x00000001???0x00000000??1420382629??
18. ???0x07????9????0x00??0x0593??0x0002??0x0000.0035de5e??0x00c02692??0x0000.000.00000000??0x00000001???0x00000000??1420381815??
19. ???0x08????9????0x00??0x0594??0x000a??0x0000.0035e089??0x00c02693??0x0000.000.00000000??0x00000001???0x00000000??1420382629??
20. ???0x09????9????0x00??0x0592??0x001d??0x0000.0035df03??0x00c02692??0x0000.000.00000000??0x00000001???0x00000000??1420382080??
21. ???0x0a????9????0x00??0x0593??0x0011??0x0000.0035e0b8??0x00c02694??0x0000.000.00000000??0x00000001???0x00000000??1420382639??
22. ???0x0b???10????0x80??0x0595??0x0003??0x0000.00000000??0x00c02694??0x0000.000.00000000??0x00000001???0x00000000??0??
23. ???0x0c????9????0x00??0x0594??0x001c??0x0000.0035dfad??0x00c02693??0x0000.000.00000000??0x00000001???0x00000000??1420382440??
24. ???0x0d????9????0x00??0x0592??0x0014??0x0000.0035ddac??0x00c02692??0x0000.000.00000000??0x00000001???0x00000000??1420381705??
25. .....??
26. *-----------------------------??
27. *?Rec?#0x1d??slt:?0x0b??objn:?77560(0x00012ef8)??objd:?77560??tblspc:?0(0x00000000)??
28. *???????Layer:??11?(Row)???opc:?1???rci?0x00?????
29. Undo?type:??Regular?undo????Begin?trans????Last?buffer?split:??No???
30. Temp?Object:??No???
31. Tablespace?Undo:??No???
32. rdba:?0x00000000Ext?idx:?0??
33. flg2:?0??
34. *-----------------------------??
35. uba:?0x00c02694.0109.1c?ctl?max?scn:?0x0000.0035dc32?prv?tx?scn:?0x0000.0035dc72??
36. txn?start?scn:?scn:?0x0000.0035e1d6?logon?user:?0??
37. ?prev?brb:?12592785?prev?bcl:?0??
38. KDO?undo?record:??
39. KTB?Redo???
40. op:?0x03??ver:?0x01????
41. compat?bit:?4?(post-11)?padding:?0??
42. op:?Z??
43. KDO?Op?code:?URP?row?dependencies?Disabled??
44. ??xtype:?XA?flags:?0x00000000??bdba:?0x00416169??hdba:?0x00416168??
45. itli:?2??ispac:?0??maxfr:?4863??
46. tabn:?0?slot:?0(0x0)?flag:?0x2c?lock:?0?ckix:?0??
47. ncol:?2?nnew:?1?size:?-1??
48. col??1:?[?2]??c1?02??
49. ???
50. *-----------------------------??
51. *?Rec?#0x1e??slt:?0x0b??objn:?77560(0x00012ef8)??objd:?77560??tblspc:?0(0x00000000)??
52. *???????Layer:??11?(Row)???opc:?1???rci?0x1d?????
53. Undo?type:??Regular?undo???Last?buffer?split:??No???
54. Temp?Object:??No???
55. Tablespace?Undo:??No???
56. rdba:?0x00000000??
57. *-----------------------------??
58. KDO?undo?record:??
59. KTB?Redo???
60. op:?0x02??ver:?0x01????
61. compat?bit:?4?(post-11)?padding:?0??
62. op:?C??uba:?0x00c02694.0109.1d--指向前一个undo记录??
63. KDO?Op?code:?URP?row?dependencies?Disabled??
64. ??xtype:?XAxtype?KDO_KDOM2?flags:?0x00000080??bdba:?0x00416169??hdba:?0x00416168??
65. itli:?2??ispac:?0??maxfr:?4863??
66. tabn:?0?slot:?0(0x0)?flag:?0x2c?lock:?2?ckix:?0??
67. ncol:?2?nnew:?1?size:?0??
68. Vector?content:???
69. col??1:?[?3]??c2?02?02??
70. ???
71. *-----------------------------??
72. *?Rec?#0x1f??slt:?0x0b??objn:?77560(0x00012ef8)??objd:?77560??tblspc:?0(0x00000000)??
73. *???????Layer:??11?(Row)???opc:?1???rci?0x1e?????
74. Undo?type:??Regular?undo???Last?buffer?split:??No???
75. Temp?Object:??No???
76. Tablespace?Undo:??No???
77. rdba:?0x00000000??
78. *-----------------------------??
79. KDO?undo?record:??
80. KTB?Redo???
81. op:?0x02??ver:?0x01????
82. compat?bit:?4?(post-11)?padding:?0??
83. op:?C??uba:?0x00c02694.0109.1e?--指向前一个undo记录??
84. </span>KDO?Op?code:?URP?row?dependencies?Disabled??
85. ??xtype:?XAxtype?KDO_KDOM2?flags:?0x00000080??bdba:?0x00416169??hdba:?0x00416168??
86. itli:?2??ispac:?0??maxfr:?4863??
87. tabn:?0?slot:?0(0x0)?flag:?0x2c?lock:?2?ckix:?0??
88. ncol:?2?nnew:?1?size:?0??
89. Vector?content:???
90. col??1:?[?3]??c2?02?03?--?这是数据块事务槽uba的地址指向的undo记录，c2?02?03代表着102，说明修改前是102.??

Oracle事务原理探究2--读书笔记五

原文：http://liwenshui322.iteye.com/blog/2172702