深入剖析一个完整的事务

oracle029

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深入剖析一个完整的事务

2、图解一个事务的操作流程
Undo段的组成：段头、回滚块
事务ID：oracle为每个事务分配事务id

select xid,xidusn,xidslot,xidsqn,ubablk,ubafil from v$transaction;//lists the active transactions in the system. null null null null null null insert into t values(1,'zhangsan'); select xid,xidusn,xidslot,xidsqn,ubablk,ubafil from v$transaction; 070017008F020000 7 23 655 1037 3//当前活动事务 COMMIT select xid,xidusn,xidslot,xidsqn,ubablk,ubafil from v$transaction; null null null null null null//说明事务已经被提交了

事务表
undo段的第一个数据块，每一个回滚段最多可以47个事务

回滚段的段头块 select * from v$rollname; 0 SYSTEM 1 _SYSSMU1_3780397527$ 2 _SYSSMU2_2232571081$ 3 _SYSSMU3_2097677531$ 4 _SYSSMU4_1152005954$ 5 _SYSSMU5_1527469038$ 6 _SYSSMU6_2443381498$ 7 _SYSSMU7_3286610060$ 8 _SYSSMU8_2012382730$ 9 _SYSSMU9_1424341975$ 10 _SYSSMU10_3550978943$ select header_block,header_file from dba_segments where segment_name='_SYSSMU1_3780397527$'; 128 3 alter system dump undo header '_SYSSMU1_3780397527$';//转储回滚段头 查看当前会话的进程编号 select spid from v$process where addr in (select paddr from v$session where sid=(select sid from v$mystat where rownum=1)); spid//server process ID 5179 alter system dump undo header '_SYSSMU1_3780397527$';//转储回滚段 alter system dump datafile 5 block 4308;//转储回滚段数据块

1. 一个事务的开始要在undo的段头块的事务表中写事务信息XID，而且还要在将要被修改的数据块的事务槽中

写事务信息XID。

事务槽：xid（需要修改的块的事务槽）、uba（是修改原数据存在于undo中的数据块的地址信息）

深入剖析事务槽和事务的提交方式

7、事务槽ITL
默认是1
最大255（从Oracle10g开始不能更改）

DBA_TABLESdescribes all relational tables in the database. USER_TABLESdescribes the relational tables owned by the current user. This view does not display theOWNERcolumn. SQL> select INI_TRANS,MAX_TRANS from dba_tables where table_name='T'; INI_TRANS MAX_TRANS ---------- ---------- 1 255

事务槽争用
create table t(id number(5),name char(2000));
insert into t values(1,'aa');
insert into t values(2,'bb');
insert into t values(3,'bb');
insert into t values(4,'cc');
insert into t values(5,'dd');
commit;
select dbms_rowid.rowid_relative_fno(rowid),dbms_rowid.rowid_block_number(rowid),id from t;

DBMS_ROWID.ROWID_RELATIVE_FNO(ROWID), DBMS_ROWID.ROWID_BLOCK_NUMBER(ROWID), ID

1 86193 1//某条记录所对应的文件编号和块号
1 86193 1
1 86193 2
1 86193 3
1 86193 4
1 86193 5

update t10 set name='abcd' where id=1;
select ubafil,ubablk,xidusn,xidslot,xidsqn,start_scnb from v$transaction;

UBAFIL, UBABLK, XIDUSN, XIDSLOT, XIDSQN, START_SCNB 3 11254919 868 1234672 //UBA的文件号，块号，回滚块的段头块，表中的哪一行记录，记录被覆盖第几次（这些信息既存在事务表中也存在事务操作中）

select * from v$rollname ;//查询段头块

0 SYSTEM 1 _SYSSMU1_3780397527$ 2 _SYSSMU2_2232571081$ 3 _SYSSMU3_2097677531$ 4 _SYSSMU4_1152005954$ 5 _SYSSMU5_1527469038$ 6 _SYSSMU6_2443381498$ 7 _SYSSMU7_3286610060$ 8 _SYSSMU8_2012382730$ 9 _SYSSMU9_1424341975$ 10 _SYSSMU10_3550978943$

SQL> select spid from v$process where addr in (select paddr from v$session where sid=(select sid from v$mystat where rownum=1)); 2 SPID ------------------------ 11175//通过server Pro来到udump中查找对应的文件

alter system dump undo header '_SYSSMU8_2012382730$';

SQL> show parameter dump NAME TYPE VALUE ------------------------------------ ----------- ------------------------------ background_core_dump string partial background_dump_dest string /u01/app/oracle/diag/rdbms/jia gulun/jiagulun/trace core_dump_dest string /u01/app/oracle/diag/rdbms/jia gulun/jiagulun/cdump max_dump_file_size string unlimited shadow_core_dump string partial user_dump_dest string /u01/app/oracle/diag/rdbms/jia gulun/jiagulun/trace SQL>

[oracle@localhost trace]$ cat jiagulun_ora_11175.trc Trace file /u01/app/oracle/diag/rdbms/jiagulun/jiagulun/trace/jiagulun_ora_11175.trc Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production With the Partitioning, OLAP, Data Mining and Real Application Testing options ORACLE_HOME = /u01/app/product/11.2.0/db_1 System name: Linux Node name: localhost.localdomain Release: 2.6.18-194.el5 Version: #1 SMP Tue Mar 16 21:52:39 EDT 2010 Machine: x86_64 Instance name: jiagulun Redo thread mounted by this instance: 1 Oracle process number: 29 Unix process pid: 11175, image: [email protected] (TNS V1-V3) *** 2015-01-03 00:05:56.449 *** SESSION ID:(36.245) 2015-01-03 00:05:56.449 *** CLIENT ID:() 2015-01-03 00:05:56.449 *** SERVICE NAME:(SYS$USERS) 2015-01-03 00:05:56.449 *** MODULE NAME:([email protected] (TNS V1-V3)) 2015-01-03 00:05:56.449 *** ACTION NAME:() 2015-01-03 00:05:56.449 ******************************************************************************** Undo Segment: _SYSSMU8_2012382730$ (8) ******************************************************************************** Extent Control Header ----------------------------------------------------------------- Extent Header:: spare1: 0 spare2: 0 #extents: 3 #blocks: 143 last map 0x00000000 #maps: 0 offset: 4080 Highwater:: 0x00c000fc ext#: 1 blk#: 4 ext size: 8 #blocks in seg. hdr's freelists: 0 #blocks below: 0 mapblk 0x00000000 offset: 1 Unlocked Map Header:: next 0x00000000 #extents: 3 obj#: 0 flag: 0x40000000 Extent Map ----------------------------------------------------------------- 0x00c000f1 length: 7 0x00c000f8 length: 8 0x00c02c00 length: 128 Retention Table ----------------------------------------------------------- Extent Number:0 Commit Time: 1420272055 Extent Number:1 Commit Time: 1420272055 Extent Number:2 Commit Time: 1420267116 TRN CTL:: seq: 0x00b3 chd: 0x001b ctl: 0x0020 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x00c000fc.00b3.09 scn: 0x0000.0013265c Version: 0x01 FREE BLOCK POOL:: uba: 0x00c000fc.00b3.0b ext: 0x1 spc: 0x1a54 uba: 0x00c000fa.00b3.33 ext: 0x1 spc: 0x680 uba: 0x00000000.00b1.2d ext: 0x2 spc: 0x11bc uba: 0x00000000.0000.00 ext: 0x0 spc: 0x0 uba: 0x00000000.0000.00 ext: 0x0 spc: 0x0 TRN TBL:: index state cflags wrap# uel scn dba parent-xid nub stmt_num cmt ------------------------------------------------------------------------------------------------ 0x00 9 0x00 0x0355 0x0016 0x0000.00132a0f 0x00c000f6 0x0000.000.00000000 0x00000001 0x00000000 1420272011 .... . ... .... ... ...... .... .... .... ... .... 0x20 9 0x00 0x0355 0xffff 0x0000.00132b09 0x00c000fc 0x0000.000.00000000 0x00000001 0x00000000 1420272233 0x21 9 0x00 0x0354 0x000a 0x0000.00132900 0x00c000f6 0x0000.000.00000000 0x00000001 0x00000000 1420271514 EXT TRN CTL:: usn: 8 sp1:0x00000000 sp2:0x00000000 sp3:0x00000000 sp4:0x00000000 sp5:0x00000000 sp6:0x00000000 sp7:0x7fff00000000 sp8:0x00000000 EXT TRN TBL:: index extflag extHash extSpare1 extSpare2 --------------------------------------------------- 0x00 0x00000000 0x00000000 0x00000000 0x00000000 ... ..... ..... .... ... 0x21 0x00000000 0x00000000 0x00000000 0x00000000 [oracle@localhost trace]$

alter system dump datafile 3 block11254; // 回滚块，数据块