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
点击(此处)折叠或打开
gyj@ZMDB>select*from v$type_size where componentin('KCB','KTB');
COMPONENTYPEDESCRIPTION TYPE_SIZE
----------------------------------------------------------
KCB KCBH BLOCK COMMON HEADER 20
KTB KTBIT TRANSACTION VARIABLE HEADER 24
KTB KTBBH TRANSACTION FIXED HEADER 48
KTB KTBBH_BS TRANSACTION BLOCK BITMAP SEGMENT 8
1、我们先对ASSM做测试
点击(此处)折叠或打开
gyj@ZMDB>select*from v$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'size50M;
Tablespace created.
gyj@ZMDB>create table gyj_t5(idint,namevarchar2(100))tablespace assm;
Table created.
gyj@ZMDB>insertintogyj_t5 values(1,'AAAAA');
1 row created.
gyj@ZMDB>insertintogyj_t5 values(2,'BBBBB');
1 row created.
gyj@ZMDB>insertintogyj_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,namefrom gyj_t5;
FILE# BLOCK# IDNAME
----------------------------------------
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
点击(此处)折叠或打开
gyj@ZMDB>create tablespace mssm datafile'/u01/app/oracle/oradata/zmdb/mssm01.dbf'size50M segment space management manual;
Tablespace created.
gyj@ZMDB>create table gyj_mssm(idint,namevarchar2(100))tablespace mssm;
Table created.
gyj@ZMDB>insertintogyj_mssm values(4,'DDDDD');
1 row created.
gyj@ZMDB>insertintogyj_mssm values(5,'EEEEE');
1 row created.
gyj@ZMDB>insertintogyj_mssm values(6,'FFFFF');
1 row created.
gyj@ZMDB>commit;
Commit complete.
gyj@ZMDB>colnamefora20
gyj@ZMDB>select dbms_rowid.rowid_relative_fno(rowid)file#,dbms_rowid.rowid_block_number(rowid)block#,id,namefrom gyj_mssm;
FILE# BLOCK# IDNAME
--------------------------------------------------
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
点击(此处)折叠或打开
************MSSM
BBED>setfile11 block 129
FILE#11
BLOCK# 129
BBED>map/v
File:/u01/app/oracle/oradata/zmdb/mssm01.dbf(11)
Block: 129 Dba:0x02c00081
------------------------------------------------------------
KTBDataBlock(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>setfile10 block 135
FILE#10
BLOCK# 135
File:/u01/app/oracle/oradata/zmdb/assm01.dbf(10)
Block: 141 Dba:0x0280008d
------------------------------------------------------------
KTBDataBlock(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
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。
声明：本站所有文章资源内容，如无特殊说明或标注，均为采集网络资源。如若本站内容侵犯了原著者的合法权益，可联系本站删除。
