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数据块内部偏移量的基本计算方法

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Release： 2016-06-07 15:57:42
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转载请注明出处：http://blog.csdn.net/guoyjoe/article/details/32715157 BASE的计算方法为： gyj@ZMDB select * from v$type_size where component in (KCB,KTB);COMPONEN TYPE DESCRIPTION TYPE_SIZE-------- -------- --------------------------------

转载请注明出处：http://blog.csdn.net/guoyjoe/article/details/32715157

BASE的计算方法为：

<strong>gyj@ZMDB> select * from v$type_size where component in (&#39;KCB&#39;,&#39;KTB&#39;);

COMPONEN TYPE     DESCRIPTION                       TYPE_SIZE
-------- -------- -------------------------------- ----------
KCB      KCBH     BLOCK COMMON HEADER                      20
KTB      KTBIT    TRANSACTION VARIABLE HEADER              24
KTB      KTBBH    TRANSACTION FIXED HEADER                 48
KTB      KTBBH_BS TRANSACTION BLOCK BITMAP SEGMENT          8
</strong>
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1、我们先对ASSM做测试

<strong>yj@ZMDB> select * from v$version;

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

gyj@ZMDB> create tablespace assm datafile &#39;/u01/app/oracle/oradata/zmdb/assm01.dbf&#39; size 50M;

Tablespace created.

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

Table created.

gyj@ZMDB> insert into gyj_t5 values(1,&#39;AAAAA&#39;);

1 row created.

gyj@ZMDB> insert into gyj_t5 values(2,&#39;BBBBB&#39;);

1 row created.

gyj@ZMDB> insert into gyj_t5 values(3,&#39;CCCCC&#39;);

1 row created.

gyj@ZMDB> COMMIT;

Commit complete.

gyj@ZMDB> alter system flush buffer_cache;

System altered.

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

     FILE#     BLOCK#          ID   NAME
---------- ----------   ---------- ----------
        10        135          1    AAAAA
        10        135          2    BBBBB
        10        135          3    CCCCC


BBED> set file 10 block 135
        FILE#           10
        BLOCK#          135

BBED> p kdbr[0]
sb2 kdbr[0]                                 @118      8076

BBED> p *kdbr[0]
rowdata[24]
-----------
ub1 rowdata[24]                             @8176     0x2c

BBED> x /rnc
rowdata[24]                                 @8176    
-----------
flag@8176: 0x2c (KDRHFL, KDRHFF, KDRHFH)
lock@8177: 0x01
cols@8178:    2

col    0[2] @8179: 1 
col    1[5] @8182: AAAAA

BBED> p ktbbhict
sb2 ktbbhict                                @36       2

8176-8076=76+（itc-1) * 24= 76+（2-1）* 24=100
</strong>
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2、我们对MSSM做测试

gyj@ZMDB> create tablespace mssm datafile &#39;/u01/app/oracle/oradata/zmdb/mssm01.dbf&#39; size 50M segment space management manual;

Tablespace created.


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

Table created.

gyj@ZMDB> insert into gyj_mssm values(4,&#39;DDDDD&#39;);

1 row created.

gyj@ZMDB> insert into gyj_mssm values(5,&#39;EEEEE&#39;);

1 row created.

gyj@ZMDB> insert into gyj_mssm values(6,&#39;FFFFF&#39;);

1 row created.

gyj@ZMDB> commit;

Commit complete.


gyj@ZMDB> col name for a20
gyj@ZMDB> select dbms_rowid.rowid_relative_fno(rowid) file#,dbms_rowid.rowid_block_number(rowid) block#,id,name from gyj_mssm;

     FILE#     BLOCK#         ID NAME
---------- ---------- ---------- --------------------
        11        129          4 DDDDD
        11        129          5 EEEEE
        11        129          6 FFFFF

BBED> set file 11 block 129
        FILE#           11
        BLOCK#          129

BBED> p kdbr[0]
sb2 kdbr[0]                                 @110      8084

BBED> p *kdbr[0]
rowdata[24]
-----------
ub1 rowdata[24]                             @8176     0x2c

BBED> x /rnc
rowdata[24]                                 @8176    
-----------
flag@8176: 0x2c (KDRHFL, KDRHFF, KDRHFH)
lock@8177: 0x01
cols@8178:    2

col    0[2] @8179: 4 
col    1[5] @8182: DDDDD

BBED> p ktbbhict
sb2 ktbbhict                                @36       2

8176-8084=68+（itc-1) * 24=68+（2-1）*24=92
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3、为什么ASSM要比MSSM多了8个字节

************MSSM
BBED> set file 11 block 129
        FILE#           11
        BLOCK#          129

BBED> map /v
 File: /u01/app/oracle/oradata/zmdb/mssm01.dbf (11)
 Block: 129                                   Dba:0x02c00081
------------------------------------------------------------
 KTB Data Block (Table/Cluster)

 struct kcbh, 20 bytes                      @0       
    ub1 type_kcbh                           @0       
    ub1 frmt_kcbh                           @1       
    ub1 spare1_kcbh                         @2       
    ub1 spare2_kcbh                         @3       
    ub4 rdba_kcbh                           @4       
    ub4 bas_kcbh                            @8       
    ub2 wrp_kcbh                            @12      
    ub1 seq_kcbh                            @14      
    ub1 flg_kcbh                            @15      
    ub2 chkval_kcbh                         @16      
    ub2 spare3_kcbh                         @18      

 struct ktbbh, 72 bytes                     @20      
    ub1 ktbbhtyp                            @20      
    union ktbbhsid, 4 bytes                 @24      
    struct ktbbhcsc, 8 bytes                @28      
    sb2 ktbbhict                            @36      
    ub1 ktbbhflg                            @38      
    ub1 ktbbhfsl                            @39      
    ub4 ktbbhfnx                            @40      
    struct ktbbhitl[2], 48 bytes            @44      

 struct kdbh, 14 bytes                      @92      
    ub1 kdbhflag                            @92      
    sb1 kdbhntab                            @93      
    sb2 kdbhnrow                            @94      
    sb2 kdbhfrre                            @96      
    sb2 kdbhfsbo                            @98      
    sb2 kdbhfseo                            @100     
    sb2 kdbhavsp                            @102     
    sb2 kdbhtosp                            @104     

 struct kdbt[1], 4 bytes                    @106     
    sb2 kdbtoffs                            @106     
    sb2 kdbtnrow                            @108     

 sb2 kdbr[3]                                @110     

 ub1 freespace[8036]                        @116     

 ub1 rowdata[36]                            @8152    

 ub4 tailchk                                @8188

*****************ASSM
BBED> set file 10 block 135
        FILE#           10
        BLOCK#          135

File: /u01/app/oracle/oradata/zmdb/assm01.dbf (10)
 Block: 141                                   Dba:0x0280008d
------------------------------------------------------------
 KTB Data Block (Table/Cluster)

 struct kcbh, 20 bytes                      @0       
    ub1 type_kcbh                           @0       
    ub1 frmt_kcbh                           @1       
    ub1 spare1_kcbh                         @2       
    ub1 spare2_kcbh                         @3       
    ub4 rdba_kcbh                           @4       
    ub4 bas_kcbh                            @8       
    ub2 wrp_kcbh                            @12      
    ub1 seq_kcbh                            @14      
    ub1 flg_kcbh                            @15      
    ub2 chkval_kcbh                         @16      
    ub2 spare3_kcbh                         @18      

 struct ktbbh, 72 bytes                     @20      
    ub1 ktbbhtyp                            @20      
    union ktbbhsid, 4 bytes                 @24      
    struct ktbbhcsc, 8 bytes                @28      
    sb2 ktbbhict                            @36      
    ub1 ktbbhflg                            @38      
    ub1 ktbbhfsl                            @39      
    ub4 ktbbhfnx                            @40      
    struct ktbbhitl[2], 48 bytes            @44      

 struct kdbh, 14 bytes                      @100     
    ub1 kdbhflag                            @100     
    sb1 kdbhntab                            @101     
    sb2 kdbhnrow                            @102     
    sb2 kdbhfrre                            @104     
    sb2 kdbhfsbo                            @106     
    sb2 kdbhfseo                            @108     
    sb2 kdbhavsp                            @110     
    sb2 kdbhtosp                            @112     

 struct kdbt[1], 4 bytes                    @114     
    sb2 kdbtoffs                            @114     
    sb2 kdbtnrow                            @116     

 sb2 kdbr[3]                                @118     

 ub1 freespace[8028]                        @124     

 ub1 rowdata[36]                            @8152    

 ub4 tailchk                                @8188
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对比

struct kdbh, 14 bytes @92

---ASSM

struct kdbh, 14 bytes @100

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