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
-------- -------- -------------------------------- ----------
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

1、我们先对ASSM做测试

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 '/u01/app/oracle/oradata/zmdb/assm01.dbf' 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,'AAAAA');

1 row created.

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

1 row created.

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

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

2、我们对MSSM做测试

gyj@ZMDB> create tablespace mssm datafile '/u01/app/oracle/oradata/zmdb/mssm01.dbf' 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,'DDDDD');

1 row created.

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

1 row created.

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

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

3、为什么ASSM要比MSSM多了8个字节