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数据块内部偏移量的基本计算方法
转载请注明出处：http://blog.csdn.net/guoyjoe/article/details/32715157
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
gyj@ZMDB> select * from v$type_size where component in (‘KCB‘,‘KTB‘);COMPONEN TYPE DESCRIPTION TYPE_SIZE-------- -------- -------------------------------- ----------KCB KCBH BLOCK COMMON HEADER 20KTB KTBIT TRANSACTION VARIABLE HEADER 24KTB KTBBH TRANSACTION FIXED HEADER 48KTB KTBBH_BS TRANSACTION BLOCK BITMAP SEGMENT 8
1、我们先对ASSM做测试
yj@ZMDB> select * from v$version;BANNER--------------------------------------------------------------------------------Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Productiongyj@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 CCCCCBBED> set file 10 block 135 FILE# 10 BLOCK# 135BBED> p kdbr[0]sb2 kdbr[0] @118 8076BBED> p *kdbr[0]rowdata[24]-----------ub1 rowdata[24] @8176 0x2cBBED> x /rncrowdata[24] @8176 -----------flag@8176: 0x2c (KDRHFL, KDRHFF, KDRHFH)lock@8177: 0x01cols@8178: 2col 0[2] @8179: 1 col 1[5] @8182: AAAAABBED> p ktbbhictsb2 ktbbhict @36 28176-8076=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 a20gyj@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 FFFFFBBED> set file 11 block 129 FILE# 11 BLOCK# 129BBED> p kdbr[0]sb2 kdbr[0] @110 8084BBED> p *kdbr[0]rowdata[24]-----------ub1 rowdata[24] @8176 0x2cBBED> x /rncrowdata[24] @8176 -----------flag@8176: 0x2c (KDRHFL, KDRHFF, KDRHFH)lock@8177: 0x01cols@8178: 2col 0[2] @8179: 4 col 1[5] @8182: DDDDDBBED> p ktbbhictsb2 ktbbhict @36 28176-8084=68+（itc-1) * 24=68+（2-1）*24=92
3、为什么ASSM要比MSSM多了8个字节
************MSSMBBED> set file 11 block 129 FILE# 11 BLOCK# 129BBED> 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*****************ASSMBBED> set file 10 block 135 FILE# 10 BLOCK# 135File: /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
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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