惜分飞

有一个朋友找到我,说数据库重启之后无法正常启动,提示ORA-00959 UNDOTBS1表空间不存在

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在数据库的启动过程中,这个是一个很常见的错误,一般出现这类错误的原因是由于undo_tablespace指定的undo表空间不存在导致.但是这个库比较明显,设置了undo_management=manual, undo_tablespace=system,依旧数据库需要找undotbs1表空间,进一步分析数据库当前表空间情况

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该数据库确实没有undotbs1表空间,基于以上信息,初步怀疑很可能是undo回滚段异常,通过对于oracle基表进行分析,发现信息

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基于上面的信息,可以确认回滚段中确实有四条记录指向被删除的undotbs1,而且还有一条undo回滚段信息为need recovery状态.进一步分析数据库alert日志

--创建undotbs2表空间,并重启数据库
Sun Sep 26 14:42:16 2021
create undo tablespace UNDOTBS2 datafile '/data/oradata/xifenfei/undotbs001.dbf' size 120G
reuse autoextend on next 500m maxsize unlimited
Sun Sep 26 14:46:46 2021
Completed: create undo tablespace UNDOTBS2 datafile '/data/oradata/xifenfei/undotbs001.dbf' size 120G
reuse autoextend on next 500m maxsize unlimited
Sun Sep 26 14:47:13 2021
[16927] Successfully onlined Undo Tablespace 10.
[16927] **** active transactions found in undo Tablespace 2 - moved to Pending Switch-Out state.
[16927] active transactions found/affinity dissolution incompletein undo tablespace 2 during switch-out.
ALTER SYSTEM SET undo_tablespace='UNDOTBS2' SCOPE=BOTH;
Sun Sep 26 14:49:25 2021
Shutting down instance (immediate)
Shutting down instance: further logons disabled
Stopping background process QMNC

---第一次尝试删除undotbs1失败
Sun Sep 26 15:06:30 2021
drop tablespace UNDOTBS1 INCLUDING CONTENTS AND DATAFILES CASCADE CONSTRAINTS
Sun Sep 26 15:47:26 2021
ORA-1013 signalled during: drop tablespace UNDOTBS1 INCLUDING CONTENTS AND DATAFILES CASCADE CONSTRAINTS
...
Sun Sep 26 15:48:40 2021
Shutting down instance (immediate)
Shutting down instance: further logons disabled
Stopping background process QMNC

--加上该隐含参数,继续重启库删除undotbs1,依旧删除失败
  _corrupted_rollback_segments= "_SYSSMU28_1306132068$"

Sun Sep 26 15:53:34 2021
QMNC started with pid=31, OS id=20454 
Completed: ALTER DATABASE OPEN
Sun Sep 26 15:55:32 2021
 drop tablespace UNDOTBS1 INCLUDING CONTENTS AND DATAFILES CASCADE CONSTRAINTS
…………
Sun Sep 26 16:45:47 2021
ORA-1013 signalled during:  drop tablespace UNDOTBS1 INCLUDING CONTENTS AND DATAFILES CASCADE CONSTRAINTS...
Sun Sep 26 16:46:00 2021
Shutting down instance (immediate)
Shutting down instance: further logons disabled
Stopping background process QMNC

---加上以下参数，并尝试重启数据库删除undotbs1成功
  _corrupted_rollback_segments= "_SYSSMU31_201790566$"
  _corrupted_rollback_segments= "_SYSSMU30_2395098326$"
  _corrupted_rollback_segments= "_SYSSMU29_306369076$"
  _corrupted_rollback_segments= "_SYSSMU28_1306132068$"

Sun Sep 26 16:47:24 2021
QMNC started with pid=31, OS id=23421 
Completed: ALTER DATABASE OPEN
Sun Sep 26 16:47:40 2021
drop tablespace UNDOTBS1 INCLUDING CONTENTS AND DATAFILES CASCADE CONSTRAINTS
…………
Mon Sep 27 01:44:56 2021
Deleted file /data/oradata/xifenfei/undotbs01.dbf
Deleted file /data/oradata/xifenfei/undotbs02.dbf
Deleted file /data/oradata/xifenfei/undotbs03.dbf
Deleted file /data/oradata/xifenfei/undotbs04.dbf
Deleted file /data/oradata/xifenfei/undotbs05.dbf
Deleted file /data/oradata/xifenfei/undotbs06.dbf
Completed: drop tablespace UNDOTBS1 INCLUDING CONTENTS AND DATAFILES CASCADE CONSTRAINTS

从这里基本上可以看出来,操作之人非常草率,在oracle回滚段还在被占用状态,直接尝试删除老undo表空间,在无法删除之后,直接暴力的使用undo回滚段异常参数,然后进行undo表空间删除.这样操作的后果屏蔽了事务的一致性,导致后续可能导致数据库一系列异常.对当前库启动过程进行跟踪发现

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数据库启动的过程中查询undo$中的undotbs1信息,而该表空间不存在,所以出现此类报错,从而导致数据库无法正常启动.知道问题原因所在,那通过undo$记录,数据库即可正常启动.