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数据块内部偏移量的基本计算方法

BASE的计算方法为：
对于ASSM：76+（itc-1) * 24= 52 + itc * 24
对于MSSM：68+（itc-1) * 24= 44 + itc * 24


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  1. gyj@ZMDB> select * from v$type_size where component in ('KCB','KTB');

  3. COMPONEN TYPE DESCRIPTION TYPE_SIZE

  4. -------- -------- -------------------------------- ----------

  5. KCB KCBH BLOCK COMMON HEADER 20

  6. KTB KTBIT TRANSACTION VARIABLE HEADER 24

  7. KTB KTBBH TRANSACTION FIXED HEADER 48

  8. KTB KTBBH_BS TRANSACTION BLOCK BITMAP SEGMENT 8


1、我们先对ASSM做测试

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  1. gyj@ZMDB> select * from v$version;

  3. BANNER

  4. --------------------------------------------------------------------------------

  5. Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production

  7. gyj@ZMDB> create tablespace assm datafile '/u01/app/oracle/oradata/zmdb/assm01.dbf' size 50M;

  9. Tablespace created.

  11. gyj@ZMDB> create table gyj_t5(id int,name varchar2(100)) tablespace assm;

  13. Table created.

  15. gyj@ZMDB> insert into gyj_t5 values(1,'AAAAA');

  17. 1 row created.

  19. gyj@ZMDB> insert into gyj_t5 values(2,'BBBBB');

  21. 1 row created.

  23. gyj@ZMDB> insert into gyj_t5 values(3,'CCCCC');

  25. 1 row created.

  27. gyj@ZMDB> COMMIT;

  29. Commit complete.

  31. gyj@ZMDB> alter system flush buffer_cache;

  33. System altered.

  35. gyj@ZMDB> select dbms_rowid.rowid_relative_fno(rowid) file#,dbms_rowid.rowid_block_number(rowid) block#,id,name from gyj_t5;

  37.      FILE# BLOCK# ID NAME

  38. ---------- ---------- ---------- ----------

  39.         10 135 1 AAAAA

  40.         10 135 2 BBBBB

  41.         10 135 3 CCCCC

  44. BBED> set file 10 block 135

  45.         FILE# 10

  46.         BLOCK# 135

  48. BBED> p kdbr[0]

  49. sb2 kdbr[0] @118 8076

  51. BBED> p *kdbr[0]

  52. rowdata[24]

  53. -----------

  54. ub1 rowdata[24] @8176 0x2c

  56. BBED> x /rnc

  57. rowdata[24] @8176 

  58. -----------

  59. flag@8176: 0x2c (KDRHFL, KDRHFF, KDRHFH)

  60. lock@8177: 0x01

  61. cols@8178: 2

  63. col 0[2] @8179: 1 

  64. col 1[5] @8182: AAAAA

  66. BBED> p ktbbhict

  67. sb2 ktbbhict @36 2

  69. 8176-8076=76+（itc-1) * 24= 76+（2-1）* 24=100


2、我们对MSSM做测试

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  1. gyj@ZMDB> create tablespace mssm datafile '/u01/app/oracle/oradata/zmdb/mssm01.dbf' size 50M segment space management manual;

  3. Tablespace created.

  6. gyj@ZMDB> create table gyj_mssm(id int,name varchar2(100)) tablespace mssm;

  8. Table created.

  10. gyj@ZMDB> insert into gyj_mssm values(4,'DDDDD');

  12. 1 row created.

  14. gyj@ZMDB> insert into gyj_mssm values(5,'EEEEE');

  16. 1 row created.

  18. gyj@ZMDB> insert into gyj_mssm values(6,'FFFFF');

  20. 1 row created.

  22. gyj@ZMDB> commit;

  24. Commit complete.

  27. gyj@ZMDB> col name for a20

  28. gyj@ZMDB> select dbms_rowid.rowid_relative_fno(rowid) file#,dbms_rowid.rowid_block_number(rowid) block#,id,name from gyj_mssm;

  30.      FILE# BLOCK# ID NAME

  31. ---------- ---------- ---------- --------------------

  32.         11 129 4 DDDDD

  33.         11 129 5 EEEEE

  34.         11 129 6 FFFFF

  36. BBED> set file 11 block 129

  37.         FILE# 11

  38.         BLOCK# 129

  40. BBED> p kdbr[0]

  41. sb2 kdbr[0] @110 8084

  43. BBED> p *kdbr[0]

  44. rowdata[24]

  45. -----------

  46. ub1 rowdata[24] @8176 0x2c

  48. BBED> x /rnc

  49. rowdata[24] @8176 

  50. -----------

  51. flag@8176: 0x2c (KDRHFL, KDRHFF, KDRHFH)

  52. lock@8177: 0x01

  53. cols@8178: 2

  55. col 0[2] @8179: 4 

  56. col 1[5] @8182: DDDDD

  58. BBED> p ktbbhict

  59. sb2 ktbbhict @36 2

  61. 8176-8084=68+（itc-1) * 24=68+（2-1）*24=92


3、为什么ASSM要比MSSM多了8个字节

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  1. ************MSSM

  2. BBED> set file 11 block 129

  3.         FILE# 11

  4.         BLOCK# 129

  6. BBED> map /v

  7.  File: /u01/app/oracle/oradata/zmdb/mssm01.dbf (11)

  8.  Block: 129 Dba:0x02c00081

  9. ------------------------------------------------------------

  10.  KTB Data Block (Table/Cluster)

  12.  struct kcbh, 20 bytes @0 

  13.     ub1 type_kcbh @0 

  14.     ub1 frmt_kcbh @1 

  15.     ub1 spare1_kcbh @2 

  16.     ub1 spare2_kcbh @3 

  17.     ub4 rdba_kcbh @4 

  18.     ub4 bas_kcbh @8 

  19.     ub2 wrp_kcbh @12 

  20.     ub1 seq_kcbh @14 

  21.     ub1 flg_kcbh @15 

  22.     ub2 chkval_kcbh @16 

  23.     ub2 spare3_kcbh @18 

  25.  struct ktbbh, 72 bytes @20 

  26.     ub1 ktbbhtyp @20 

  27.     union ktbbhsid, 4 bytes @24 

  28.     struct ktbbhcsc, 8 bytes @28 

  29.     sb2 ktbbhict @36 

  30.     ub1 ktbbhflg @38 

  31.     ub1 ktbbhfsl @39 

  32.     ub4 ktbbhfnx @40 

  33.     struct ktbbhitl[2], 48 bytes @44 

  35.  struct kdbh, 14 bytes @92 

  36.     ub1 kdbhflag @92 

  37.     sb1 kdbhntab @93 

  38.     sb2 kdbhnrow @94 

  39.     sb2 kdbhfrre @96 

  40.     sb2 kdbhfsbo @98 

  41.     sb2 kdbhfseo @100 

  42.     sb2 kdbhavsp @102 

  43.     sb2 kdbhtosp @104 

  45.  struct kdbt[1], 4 bytes @106 

  46.     sb2 kdbtoffs @106 

  47.     sb2 kdbtnrow @108 

  49.  sb2 kdbr[3] @110 

  51.  ub1 freespace[8036] @116 

  53.  ub1 rowdata[36] @8152 

  55.  ub4 tailchk @8188

  57. *****************ASSM

  58. BBED> set file 10 block 135

  59.         FILE# 10

  60.         BLOCK# 135

  62. File: /u01/app/oracle/oradata/zmdb/assm01.dbf (10)

  63.  Block: 141 Dba:0x0280008d

  64. ------------------------------------------------------------

  65.  KTB Data Block (Table/Cluster)

  67.  struct kcbh, 20 bytes @0 

  68.     ub1 type_kcbh @0 

  69.     ub1 frmt_kcbh @1 

  70.     ub1 spare1_kcbh @2 

  71.     ub1 spare2_kcbh @3 

  72.     ub4 rdba_kcbh @4 

  73.     ub4 bas_kcbh @8 

  74.     ub2 wrp_kcbh @12 

  75.     ub1 seq_kcbh @14 

  76.     ub1 flg_kcbh @15 

  77.     ub2 chkval_kcbh @16 

  78.     ub2 spare3_kcbh @18 

  80.  struct ktbbh, 72 bytes @20 

  81.     ub1 ktbbhtyp @20 

  82.     union ktbbhsid, 4 bytes @24 

  83.     struct ktbbhcsc, 8 bytes @28 

  84.     sb2 ktbbhict @36 

  85.     ub1 ktbbhflg @38 

  86.     ub1 ktbbhfsl @39 

  87.     ub4 ktbbhfnx @40 

  88.     struct ktbbhitl[2], 48 bytes @44 

  90.  struct kdbh, 14 bytes @100 

  91.     ub1 kdbhflag @100 

  92.     sb1 kdbhntab @101 

  93.     sb2 kdbhnrow @102 

  94.     sb2 kdbhfrre @104 

  95.     sb2 kdbhfsbo @106 

  96.     sb2 kdbhfseo @108 

  97.     sb2 kdbhavsp @110 

  98.     sb2 kdbhtosp @112 

  100.  struct kdbt[1], 4 bytes @114 

  101.     sb2 kdbtoffs @114 

  102.     sb2 kdbtnrow @116 

  104.  sb2 kdbr[3] @118 

  106.  ub1 freespace[8028] @124 

  108.  ub1 rowdata[36] @8152 

  110.  ub4 tailchk @8188


对比
-----MSSM
   struct ktbbhitl[2], 48 bytes            @44     

 struct kdbh, 14 bytes                     @92 

---ASSM   
   struct ktbbhitl[2], 48 bytes            @44     

 struct kdbh, 14 bytes                      @100 
 
@92---->@100  kdbh偏移量发生了变化，增加了8个byte。


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