Data Block是数据库中最小的I/O单元，下面我来简单介绍下数据块的基本结构。
OK！跟着我一步步实验：
一、建表空间
SQL>create tablespace tp1 datafile '/oradata/bxocp/tp01.dbf' size 10M;
二、建用户及授权
SQL>create user gyj identified by gyj default tablespace tp1;
SQL>grant dba to gyj;
三、建表
SQL>conn gyj/gyj
SQL>create table t1 (id int,name varchar2(100));
四、插入一行数据
SQL>insert into t1 values(1,'AAAAA');
SQL>commit;
五、手动发生一个检查点，使上面一行数据写到数据文件
alter system checkpoint;
六、查这行数据所在的文件号和块号
SQL>col name for a10
SQL>select id,name,dbms_rowid.rowid_relative_fno(rowid) file#,dbms_rowid.rowid_block_number(rowid) block# from t1;
ID NAME FILE# BLOCK#
---------- --------- ---------- ----------
1 AAAAA 6 135
七、转储6号文件135号块，新开个窗口
[oracle@guoyj ~]$ sqlplus / as sysdba
SQL> alter system dump datafile 6 block 135;
八、找到转储的文件
SQL> show parameter dump
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
background_core_dump string partial
background_dump_dest string /u01/app/oracle/diag/rdbms/bxo
cp/bxocp/trace
再开一新窗口
[oracle@guoyj ~]$ cd /u01/app/oracle/diag/rdbms/bxocp/bxocp/trace
[oracle@guoyj trace]$ ls -lFtr
下面这个跟踪日志就是6号文件135号块转储出来的数据块信息
-rw-r----- 1 oracle oinstall 3363 Dec 11 18:02 bxocp_ora_5429.trc -
九、分析数据块结构
[oracle@guoyj trace]$ vi bxocp_ora_5429.trc
Trace file /u01/app/oracle/diag/rdbms/bxocp/bxocp/trace/bxocp_ora_5429.trc
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
ORACLE_HOME = /u01/app/oracle/product/11.2.0
System name: Linux
Node name: guoyj
Release: 2.6.18-128.el5
Version: #1 SMP Wed Dec 17 11:41:38 EST 2008
Machine: x86_64
VM name: VMWare Version: 6
Instance name: bxocp
Redo thread mounted by this instance: 1
Oracle process number: 28
Unix process pid: 5429, image: oracle@guoyj (TNS V1-V3)
*** 2012-12-11 18:02:31.307
*** SESSION ID:(29.15) 2012-12-11 18:02:31.307
*** CLIENT ID:() 2012-12-11 18:02:31.307
*** SERVICE NAME:(SYS$USERS) 2012-12-11 18:02:31.307
*** MODULE NAME:(sqlplus@guoyj (TNS V1-V3)) 2012-12-11 18:02:31.307
*** ACTION NAME:() 2012-12-11 18:02:31.307
Start dump data blocks tsn: 7 file#:6 minblk 135 maxblk 135