Oracle11g温习-第十一章：管理undo

Posted 2020-10-07 ORACLE-fans

2013年4月27日 星期六

10:40

 

1、undo tablespace 功能

undo tablespace 功能：用来存放从datafiles 读出的数据块旧的镜像           【             1)   回滚事务：rollback             2)   读一致性：正在做DML操作的数据块，在没有提交前，其他用户不能读，其他用户读undo里面的数据块信息             3)   事务的恢复：instance recover   (undo -------->rollback)             4)   倒序查询：flashback query、flashback table          】

2、undo 的管理模式

1)   manaual 手工：roll segment 2)   auto  自动：      undo tablespace ( init parameter ：undo_management  = auto) ，自动创建undo段

3、undo 表空间管理

1)【建立新的undo表空间（处于active状态的undo tablespace 不能offline 和 drop),可以建立多个undo表空间，但一个时刻只有一个处于active 】   SYS @ prod > create undo tablespace        undotbs2     datafile ‘/u01/app/oracle/oradata/orcl/undotbs02.dbf‘        size 100m         autoextend on next     10m maxsize 500m;                                       创建自动扩展的undo表空间     Tablespace created.    SYS @ prod >  select tablespace_name,status,contents from dba_tablespaces;   TABLESPACE_NAME                STATUS    CONTENTS ------------------------------ --------- --------- SYSTEM                                    ONLINE    PERMANENT UNDOTBS                                ONLINE    UNDO SYSAUX                                     ONLINE    PERMANENT TEMP                                        ONLINE    TEMPORARY USERS                                       ONLINE    PERMANENT UNDOTBS02                            ONLINE    UNDO        2)查看当前正在使用的undo tablespace        SYS @ prod > show parameter undo   NAME                                          TYPE                              VALUE ------------------------------------ --------------------------------- ------------------------------ undo_management                  string                            AUTO undo_retention                         integer                           900 undo_tablespace                      string                            UNDOTBS           3)切换undo表空间    SYS @ prod >alter system set undo_tablespace=undotbs2;      System altered.    SYS @ prod > show parameter undo   NAME                                 TYPE                              VALUE ------------------------------------ --------------------------------- ------------------------------ undo_management                      string                            AUTO undo_retention                       integer                           900 undo_tablespace                      string                            UNDOTBS02       4)删除undo tablespace     SYS @ prod >drop tablespace undotbs  including contents and  datafiles;     Tablespace dropped.   5) undo_retention 参数 SYS @ prod > show parameter undo;   NAME                                        TYPE                              VALUE ------------------------------------ --------------------------------- ------------------------------ undo_management                string                            AUTO undo_retention                       integer                           900 undo_tablespace                     string                            UNDOTBS   ——【undo_retention   设置当事务提交后，undo 数据块在undo tablespace空间未使用完之前的的保留时间】     SYS @ prod > alter system set undo_retention=600; SYS @ prod > show parameter undo   NAME                                 TYPE                              VALUE ------------------------------------ --------------------------------- ------------------------------ undo_management                   string                            AUTO undo_retention                       integer                           600 undo_tablespace                      string                            UNDOTBS   SYS @ prod > Alter tablespace undotbs1 retention  guarantee;【保证在retention 期间不允许被覆盖】 SYS @ prod >  Alter tablespace undotbs1 retention noguarantee;【想禁止undo表空间retention guarantee】      6)undo 表空间的大小           1)   undo_retention          2)   undo block /per second           3)   UNDO BLOCK SIZE

4、undo 信息的查询

1) v$session 【查看用户建立的session】        2) v$transaction  【当前的事务】        3) v$rollname  【回滚段的名称】        4) v$rollstat 【回滚段的状态】                   SSYS @ prod >   desc  v$session;                 SYS @ prod > select username,sid,serial# from v$session   where username is not null;   USERNAME                       SID       SERIAL# ------------------------------ ---------- ---------- SCOTT                                 141          4 SYS                                       159          3               SYS @ prod > desc  v$transaction ;    Name                                      Null?    Type  ----------------------------------------- -------- ----------------------------  ADDR                                               RAW(4)                              事务处理状态对象的地址  XIDUSN                                             NUMBER                         ——xidusn ：undo segment 的id   撤消段的号  XIDSLOT                                            NUMBER                         ——xidslot：事务槽的id    插曹号  XIDSQN                                             NUMBER                        序列号  UBAFIL                                             NUMBER                         撤消块地址（UBA)的文件号  UBABLK                                             NUMBER                        UBA 块号  UBASQN                                             NUMBER                      UBA 序列号  UBAREC                                             NUMBER                       UBA 记录号  STATUS                                             VARCHAR2(16)              状态号  START_TIME                                         VARCHAR2(20)         起始时间（挂钟)  START_SCNB                                         NUMBER                   起始系统更改号（SCN)的基点  START_SCNW                                         NUMBER                  起始SCN 包  START_UEXT                                         NUMBER                    起始区号  START_UBAFIL                                       NUMBER                  起始UBA 文件号  START_UBABLK                                       NUMBER                起始UBA 块号  START_UBASQN                                       NUMBER               起始UBA 序列号  START_UBAREC                                       NUMBER               起始记录号  SES_ADDR                                           RAW(4)                               ——SES_ADDR  当前会话的地址 FLAG                                               NUMBER                              标志位  SPACE                                              VARCHAR2(3)                    如果为空间事务处理，则为Yes  RECURSIVE                                          VARCHAR2(3)               如果为递归事务处理，则为Yes  NOUNDO                                             VARCHAR2(3)                如果为撤消事务处理，则为Yes  PTX                                                VARCHAR2(3)                        如果为并行事务处理，则为Yes，否则设为No NAME                                               VARCHAR2(256)  PRV_XIDUSN                                         NUMBER                      上一个事务处理的撤消段的号  PRV_XIDSLT                                         NUMBER                          上一个事务处理的插槽号  PRV_XIDSQN                                         NUMBER                          上一个事务处理的序列号  PTX_XIDUSN                                         NUMBER                          父级XID 的回退段号  PTX_XIDSLT                                         NUMBER                          父级XID 的插曹号  PTX_XIDSQN                                         NUMBER                         父级XID 的序列号  DSCN-B                                             NUMBER                             独立的SCN 基点  DSCN-W                                             NUMBER                            独立的SCN 包  USED_UBLK                                          NUMBER                         已用的撤消块数量  USED_UREC                                          NUMBER                         已用的撤消记录数量  LOG_IO                                             NUMBER                                逻辑I/O  PHY_IO                                             NUMBER                                物理I/O  CR_GET                                             NUMBER                                一致性获取  CR_CHANGE                                          NUMBER                         一致性更改  START_DATE                                         DATE  DSCN_BASE                                          NUMBER  DSCN_WRAP                                          NUMBER  START_SCN                                          NUMBER  DEPENDENT_SCN                                      NUMBER  XID                                                      RAW(8)  PRV_XID                                            RAW(8)  PTX_XID                                            RAW(8)                                                            SYS @ prod > select a.SID,a.SERIAL#,a.USERNAME,b.xidusn,xidslot,b.ubablk,b.status,b.name from v$session a, v$transaction  b    where a.saddr=b.ses_addr;                                                                                                                                 SID    SERIAL#       USERNAME                 XIDUSN    XIDSLOT     UBABLK    STATUS           NAME ---------- ---------- -------------------- ---------- ---------- ---------- ---------------- ----------        144            7               SCOTT                             15            26                76          ACTIVE                                                              SYS @ prod > desc  v$rollname;    【查看当前的回滚段】   ——【默认system有一个undo segment，undo tablespace 会被分配10个undo segment】   SYS @ prod > select * from v$rollname;                                                                                                            USN NAME ---------- ----------          0 SYSTEM         11 _SYSSMU11$         12 _SYSSMU12$         13 _SYSSMU13$         14 _SYSSMU14$         15 _SYSSMU15$         16 _SYSSMU16$         17 _SYSSMU17$         18 _SYSSMU18$         19 _SYSSMU19$         20 _SYSSMU20$                                                                                       SYS @ prod > select usn,extents,writes,xacts,status from v$rollstat;      【查看回滚段的状态          USN    EXTENTS     WRITES      XACTS STATUS ---------- ---------- ---------- ---------- ---------------          0          6       5560          0 ONLINE         11         10     529954          0 ONLINE         12         17    1344804          0 ONLINE         13         16     800720          0 ONLINE         14         27   11447082          1 ONLINE         15         17    1033468          0 ONLINE         16          6     307764          0 ONLINE         17         15     734590          0 ONLINE         18          8     398340          0 ONLINE         19         16     785134          0 ONLINE         20          8     407692          0 ONLINE     SYS @ prod > select a.sid,  a.serial#,  a.username,  b.xidusn,  xidslot,  b.ubablk,  b.status,  c.usn,  c.name,   d.extents,   d.writes,    d.xacts                from v$session a,v$transaction b,v$rollname c ,v$rollstat d              where a.saddr=b.ses_addr and b.xidusn=c.usn and c.usn=d.usn                                                                                                                                             SID        SERIAL#   USERNAME     XIDUSN    XIDSLOT     UBABLK     STATUS         USN     NAME            EXTENTS     WRITES          XACTS ---------- ---------- ------ ---------- ---------- ---------- ------- ---------- ---------- ---------- ---------- ------------ ---------- ---------- ------------ ----------        147         54            SCOTT                14                22              2595         ACTIVE          14    _SYSSMU14$         27           11447082                                                      【查看undo segment 数据块状态 （dba_undo_EXTENTS)】   SYS @ prod > insert into t01 values (6) ;                                                                                                  SYS @ prod > insert into t01 values (7) ;                                                                                                  SYS @ prod > create table emp1 as select * from scott.emp;                                                                                 SYS @ prod > insert into emp1 select * from emp1;                                                                                         SYS @ prod > select segment_name,tablespace_name,extent_id,file_id ,bytes/1024 ,status from dba_undo_extents                                where status like ‘%ACTIVE%‘;                                                           【查看数据库中各个undo段的状态】                                                                                        SEGMENT_NAME                   TABLESPACE_NAME                 EXTENT_ID    FILE_ID     BYTES/1024 STATUS ------------------------------ ------------------------------ ---------- ---------- ---------- ----------- ---------- ---------- ---------- _SYSSMU18$                              UNDO_TBS                                    2                     7                 64                ACTIVE _SYSSMU15$                              UNDO_TBS                                    0                     7                 64                 ACTIVE   SYS @ prod > COMMIT;                                                                                                                      Commit complete.   SYS @ prod > /                                                                                                                            SEGMENT_NAME                   TABLESPACE_NAME                 EXTENT_ID    FILE_ID BYTES/1024 STATUS ------------------------------ ------------------------------ ---------- ---------- ---------- ---------- _SYSSMU15$                     UNDO_TBS                                0          7         64 ACTIVE     【查看undo tablespace 统计信息v$undostat;】   SYS @ prod > select BEGIN_TIME,end_time,undotsn,undoblks,ACTIVEBLKS,EXPIREDBLKS,MAXQUERYID from v$undostat;                                BEGIN_TIME          END_TIME               UNDOTSN   UNDOBLKS ACTIVEBLKS EXPIREDBLKS MAXQUERYID ------------------- ------------------- ---------- ---------- ---------- ----------- ------------- 2011-08-08 10:22:35 2011-08-08 10:23:20          8          0        160         760 2011-08-08 10:12:35 2011-08-08 10:22:35          8          6        160         760 2011-08-08 10:02:35 2011-08-08 10:12:35          8        589        160           8 2011-08-08 09:52:35 2011-08-08 10:02:35          8        179        160           8 2011-08-08 09:42:35 2011-08-08 09:52:35          8         19        160           0 2011-08-08 09:32:35 2011-08-08 09:42:35          1          7        160        2840 2011-08-08 09:22:35 2011-08-08 09:32:35          1          2        160        2848 2011-08-08 09:12:35 2011-08-08 09:22:35          1          0          0           0 2011-08-08 09:02:35 2011-08-08 09:12:35          1          3          0           0   SYS @ prod > select segment_name,tablespace_name ,segment_id,file_id ,status from dba_rollback_segs;                                       SEGMENT_NAME                   TABLESPACE_NAME                SEGMENT_ID    FILE_ID STATUS ------------------------------ ------------------------------ ---------- ---------- ---------------- SYSTEM                         SYSTEM                                  0          1 ONLINE _SYSSMU1$                      RTBS                                    1          2 ONLINE _SYSSMU2$                      RTBS                                    2          2 ONLINE _SYSSMU3$                      RTBS                                    3          2 ONLINE _SYSSMU4$                      RTBS                                    4          2 ONLINE _SYSSMU5$                      RTBS                                    5          2 ONLINE _SYSSMU6$                      RTBS                                    6          2 ONLINE _SYSSMU7$                      RTBS                                    7          2 ONLINE _SYSSMU8$                      RTBS                                    8          2 ONLINE _SYSSMU9$                      RTBS                                    9          2 ONLINE _SYSSMU10$                     RTBS                                   10        2 ONLINE